The person at Michael Jackson's home who called 911 Thursday told the operator the singer wasn't breathing and wasn't conscious, according to a recording of phone call released Friday.
"I need an ambulance," the person told the 911 operator.
Police spoke with Jackson's doctor on Thursday but have been unable to reach him Friday for further questioning, the Los Angeles Police Department said.
A car the doctor was using was towed from Jackson's home Thursday and impounded, authorities said.
The car may contain "medications pertinent to the investigation" into Jackson's death, said detective Agustin Villanueva of the Los Angeles Police Department.
Police did not release the doctor's name.
Public records show the car is registered to a Texas woman who is an associate of a cardiologist. The cardiologist is licensed in California and Texas and also has an office in Las Vegas, Nevada.
CNN's calls to the doctor's office were not immediately returned.
Authorities said Friday the cause of Michael Jackson's death will not be determined officially for weeks.
The superstar's sudden death Thursday at age 50 left a family devastated, an industry stunned and legions of fans lost. It also left a glaring question: What happened?
"The likelihood is very slim that we will have any results to release today because of the extensive level of the tests that we're going to be performing," said Ed Winter, assistant chief of the Los Angeles coroners office.
The results of toxicology tests are expected in six to eight weeks, he said, adding that the cause of death will be determined when all results come in.
Initial autopsy results could show whether Jackson had an underlying heart condition, medical experts say.
There are questions over whether Jackson's death may have involved medication.
Brian Oxman, a former attorney for the Jackson family who was with the family in the hospital emergency room on Thursday, told CNN he had been concerned about medications the pop star was taking.
"I talked to this family about it, I warned them. I said that Michael is overmedicating and that I did not want to see this kind of a case develop," Oxman told CNN's "American Morning" on Friday.
He referred to Anna Nicole Smith, the former model and reality TV show star who died of an overdose in 2007.
"I said, 'If that's what's going to happen to Michael, it's all going to break our hearts.' And my worst fears are here."
Oxman emphasized that he does not know what killed Jackson, and was not making accusations against any individual.
CNN is seeking response from the family.
Jackson was in apparent cardiac arrest when paramedics rushed him Thursday from his home to Ronald Reagan UCLA Medical Center, where a team of physicians tried to resuscitate him for more than an hour, according to Jackson's brother Jermaine. He said the music idol was pronounced dead at 2:26 p.m.
The night before he had complained of not feeling well, brother Marlon Jackson said.
He told CNN on Thursday about his conversation with Jackson's manager Frank Dileo. On Wednesday night, Jackson said he was not feeling well, so his doctor went to see him. "Frank said, 'Marlon, from last night to this morning, I don't know what happened.' When they got to him this morning, he wasn't breathing."
The troubled icon had been preparing for a comeback tour, aimed at extending his legendary career and helping to pay off hundreds of millions of dollars in debt.
Michael Jackson began his professional work at age 5, singing with his brothers before shooting to superstardom as a solo artist. He had numerous No. 1 hits, the best known being "Thriller."
"Thriller" was the best-selling album of all time, at an estimated 50 million copies worldwide.
After dominating the popular music scene for years, Jackson became reclusive and mired in scandals that included child molestation charges. He was acquitted after a highly publicized trial in Santa Maria, California, in March 2006.
Last year, Jackson announced a comeback tour that was to start in July. When some of the shows were postponed till next year, rumors spread that the entertainer was weak and suffering from skin cancer.
But Marlon Jackson said he last saw his younger brother at a May 14 family gathering and he "looked great."
"He was looking well. He was getting ready to go into rehearsals for his tour. I don't know what happened," Marlon Jackson said.
The most famous of Michael Jackson's eight siblings, Janet, issued a statement through her manager.
"Janet Jackson is grief-stricken and devastated at the sudden loss of her brother," said Kenneth Crear. "She is ... flying immediately to California to be with her family."
A large crowd gathered outside the hospital, while in New York a huge crowd gathered outside the Apollo Theater.
Around the world, fans reacted with sadness.
LOS ANGELES, California (CNN) -- The person at Michael Jackson's home who called 911 Thursday told the operator the singer wasn't breathing and wasn't conscious, according to a recording of phone call released Friday.
Autopsy results may shed light into the death of pop star Michael Jackson.
1 of 3 "I need an ambulance," the person told the 911 operator.
Police spoke with Jackson's doctor on Thursday but have been unable to reach him Friday for further questioning, the Los Angeles Police Department said.
A car the doctor was using was towed from Jackson's home Thursday and impounded, authorities said.
The car may contain "medications pertinent to the investigation" into Jackson's death, said detective Agustin Villanueva of the Los Angeles Police Department.
Police did not release the doctor's name. Listen to the 911 call »
Public records show the car is registered to a Texas woman who is an associate of a cardiologist. The cardiologist is licensed in California and Texas and also has an office in Las Vegas, Nevada.
CNN's calls to the doctor's office were not immediately returned.
Authorities said Friday the cause of Michael Jackson's death will not be determined officially for weeks.
The superstar's sudden death Thursday at age 50 left a family devastated, an industry stunned and legions of fans lost. It also left a glaring question: What happened?
"The likelihood is very slim that we will have any results to release today because of the extensive level of the tests that we're going to be performing," said Ed Winter, assistant chief of the Los Angeles coroners office.
The results of toxicology tests are expected in six to eight weeks, he said, adding that the cause of death will be determined when all results come in.
Initial autopsy results could show whether Jackson had an underlying heart condition, medical experts say. Watch coroner's office discuss Jackson's death. »
There are questions over whether Jackson's death may have involved medication.
Brian Oxman, a former attorney for the Jackson family who was with the family in the hospital emergency room on Thursday, told CNN he had been concerned about medications the pop star was taking.
"I talked to this family about it, I warned them. I said that Michael is overmedicating and that I did not want to see this kind of a case develop," Oxman told CNN's "American Morning" on Friday.
He referred to Anna Nicole Smith, the former model and reality TV show star who died of an overdose in 2007.
"I said, 'If that's what's going to happen to Michael, it's all going to break our hearts.' And my worst fears are here." Watch CNN's Sanjay Gupta discuss Jackson's death »
Oxman emphasized that he does not know what killed Jackson, and was not making accusations against any individual.
CNN is seeking response from the family.
Jackson was in apparent cardiac arrest when paramedics rushed him Thursday from his home to Ronald Reagan UCLA Medical Center, where a team of physicians tried to resuscitate him for more than an hour, according to Jackson's brother Jermaine. He said the music idol was pronounced dead at 2:26 p.m. Watch crowds gather at the hospital. »
The night before he had complained of not feeling well, brother Marlon Jackson said.
He told CNN on Thursday about his conversation with Jackson's manager Frank Dileo. On Wednesday night, Jackson said he was not feeling well, so his doctor went to see him. "Frank said, 'Marlon, from last night to this morning, I don't know what happened.' When they got to him this morning, he wasn't breathing."
The troubled icon had been preparing for a comeback tour, aimed at extending his legendary career and helping to pay off hundreds of millions of dollars in debt.
Michael Jackson began his professional work at age 5, singing with his brothers before shooting to superstardom as a solo artist. He had numerous No. 1 hits, the best known being "Thriller."
"Thriller" was the best-selling album of all time, at an estimated 50 million copies worldwide.
After dominating the popular music scene for years, Jackson became reclusive and mired in scandals that included child molestation charges. He was acquitted after a highly publicized trial in Santa Maria, California, in March 2006.
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Last year, Jackson announced a comeback tour that was to start in July. When some of the shows were postponed till next year, rumors spread that the entertainer was weak and suffering from skin cancer.
But Marlon Jackson said he last saw his younger brother at a May 14 family gathering and he "looked great."
"He was looking well. He was getting ready to go into rehearsals for his tour. I don't know what happened," Marlon Jackson said.
The most famous of Michael Jackson's eight siblings, Janet, issued a statement through her manager.
"Janet Jackson is grief-stricken and devastated at the sudden loss of her brother," said Kenneth Crear. "She is ... flying immediately to California to be with her family."
A large crowd gathered outside the hospital, while in New York a huge crowd gathered outside the Apollo Theater.
Around the world, fans reacted with sadness. iReport.com: Share your Michael Jackson memories
Some, including actress Elizabeth Taylor and musician Stevie Wonder, were too distraught to issue statements.
Producer Quincy Jones, who helped Jackson craft his hit albums "Off the Wall" and "Thriller," said, "I am absolutely devastated at this tragic and unexpected news.
"For Michael to be taken away from us so suddenly at such a young age, I just don't have the words," Jones added in a statement.
Jackson's music continues to be heard throughout the world "because he had it all -- talent, grace, professionalism and dedication," Jones said. He called Jackson a consummate entertainer, whose legacy will be felt around the world.
"I've lost my little brother today and part of my soul has gone with him," Jones said.
Berry Gordy, producer and founder of Motown Records, said Jackson's death was "like a bad dream."
"As a kid, Michael was always beyond his years. He was an innovator. He was a genius at what he did," Gordy said. "He had a knowingness about him. At 9 years old, when I first started working with him, he seemed to me like he had been here before. He was just so knowledgeable about life."
Jackson's former wife, Lisa Marie Presley, said she was "shocked and saddened" by his death.
"My heart goes out to his children and his family," she said.
Jackson is survived by his three children, Prince Michael I, Paris and Prince Michael II.
