Michael Jackson''s family has been informed that a criminal investigation could be launched into the King of Pop''s death, a source close to the family told CNN on Friday.

"The family is aware of a potential criminal prosecution," the unnamed source said.

Los Angeles Police Chief William Bratton said on Thursday that investigators were waiting for the toxicology report to decide on whether Jackson''s death could have been a homicide.

In an interview with ABC News, Jackson''s 79-year-old father said he believed his son''s death was not accidental.

"I do believe it was foul play," Joe Jackson said.

The Los Angeles County coroner''s office has requested Jackson''s medical files and records from a number of doctors, as investigators try to find out whether prescription drugs played a role in the pop star''s death.

A source close to the investigation said some of the medication found in Jackson''s Holmby Hills mansion where he died on June 25 had no prescription labels, and that it was unclear how Jackson obtained them.