A three-hour autopsy of Michael Jackson on Friday turned up no signs of trauma and no foul play – and no final determination of what killed the King of Pop, leaving his family grasping for answers.

"That's what we're trying to find out right now," Jackson's father, Joe Jackson, told PEOPLE when asked about reports his son's death was tied to prescription drugs. "We're trying to find out that information. When we find it out, we'll know."

The elder Jackson hinted at troubles in the life of his son, who died Thursday at age 50 after suffering cardiac arrest at his Los Angeles home. "There's a lot to be told, though, I'll tell you that right now. The truth!" he says. "The truth is still to be told."

 

Additional Testing

He declined to elaborate, and an autopsy conducted Friday provided no clues. "The cause of death has been deferred," said Craig Harvey, operations chief for the Los Angeles County Coroner.

Additional testing, including a toxicology test for drugs in Jackson's system, will take another four to six weeks. "At that time, once those test results have been completed, we anticipate being able to close the case and issuing a final cause of death," said Harvey.

Based on the autopsy, "There was no indication of any external trauma or any indication of foul play on the body of Mr. Jackson," said Harvey. He said Jackson had been taking prescription medication, but declined to comment whether the drugs were linked to Jackson's death.

A coroner's official met with the Jackson family privately at the family compound to discuss the procedure. The body was set to be released to a mortuary Friday evening.