Los Angeles  - Michael Jackson's father alleged Friday that "foul play" led to his son's death on June 25.

Joe Jackson's comments to ABC News came amid growing indications that the criminal abuse of prescription drugs killed Jackson, and as celebrity news website tmz. com reported that at least two of Jackson's doctors were not cooperating with the coroner's request for the pop icon's medical records.

Also Friday the custody hearing to determine the guardianship of Michael Jackson's three children was postponed from July 13 to July 20, according to Los Angeles Superior Court. The postponement was made at the request of the musician's mother, Katherine Jackson, who has temporary guardianship of Jackson's three children, and the musician's ex-wife, Debbie Rowe.

Los Angeles police chief William Bratton said Thursday the case could be probed as a criminal one, and not a death investigation. "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," Bratton told 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?"

Jackson's father backed up those assertions: "I do believe it was foul play."

The Jackson family is still waiting for the results of the pop star's official autopsy and the independent autopsy. (dpa)