The Los Angeles police chief has raised the prospect of a homicide charge over the death of Michael Jackson.

Homicide does not necessarily mean murder — it could mean a manslaughter charge against a doctor.

Jackson, 50, died last month in mysterious circumstances but is reported to have been taking a cocktail of drugs including the potent anaesthetic Diprivan, also known as propofol. Los Angeles police are investigating Jackson’s prescription drug history and have subpoenaed medical records from doctors who treated him, including psychiatric records.

“We are still awaiting corroboration from the coroner’s office as to cause of death. That is going to be very dependent on the toxicology reports that are due to come back,” William Bratton, the city’s police commissioner, told the broadcaster CNN. “And based on those, we will have an idea of what it is we are dealing with. Are we dealing with a homicide? Or are we dealing with accidental overdose?

“We’ve got very good investigators. They will be prepared to deal with whatever the coroner’s findings may be.”

The singer’s father said yesterday that he suspected foul play in his son’s death. Joe Jackson, 79, said that he was dumbfounded when he learnt that his son was being taken to hospital on June 25. “I just couldn’t believe what was happening to Michael,” he told ABC News. “I do believe it was foul play. I do believe that.”

He said that a second post-mortem examination requested by the family had yet to yield answers about what killed his son. “I did not know anything about the drugs. I didn’t even know the names of them. I do know that whatever he was taking was to make him rest because he has been working so hard.

“That drug was supposed to make him relax and sleep. But anyway, he did not wake up. He never woke up. Michael died in his sleep.”

The actress Roseanne Barr said in her blog that she had been asked to call Jackson to discuss relaxation techniques.

She also described him as a long-term drug addict. “I was given his cellphone number the night before he died and asked to call him and I didn’t, I was too afraid — I thought I would wait until shabbat [the sabbath] to call him and then he was dead. He wanted to know about meditation,” she wrote. Sending her best wishes to Jackson’s three children, she added: “Their dad was a drug addict for many, many years. What makes a drug addict is someone who has too much pain in the memory banks.”

A 2004 police document, obtained by CNN, alleges that at one point Jackson was taking up to 40 pills a night of the anti-anxiety drug Xanax.

The document cites interviews with two Jackson employees in preparation for his child abuse trial, in which he was acquitted.

One of the employees, a security guard, later left his job after Jackson “fell on his face” in a hotel room. The guard said that he was not comfortable getting prescriptions for the singer, the document says.

Jackson’s body is understood to be in storage in a crypt at Forest Lawn Memorial Park, Hollywood, which is owned by Berry Gordy, the Motown Records founder, who helped to launch the Jackson 5.

The family is said to be split on the Jackson’s final resting place. His brother Jermaine wants to bury him at the Neverland Ranch, which could become a tourist magnet like Elvis Presley’s Graceland. Katherine Jackson, the family matriarch, opposes the idea because her son vowed during his child abuse investigation not to go back to Neverland.

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