Matthew Perry's cause of death could take "a couple more weeks" to be released, according to a medical examiner

He told FoxNews Digital: "They've got pretty much 99% of what they're going to get at this point as far as information goes, and they can release it now, or they can wait for a couple more weeks because they're looking for some unknown drug. They might be doing microscopic slides, but it's now about almost two weeks, so the toxicology should be finished.

"I imagine what they're doing right now is discussing the findings with the prosecutor and the family, and that in good time it will be when they should release the findings."

The '17 Again' star battled with drink and drug addictions for years before his death but police were quick to insist shortly after the tragedy that there were "no illegal drugs" found at the scene.

The doctor added: "If there are illegal drugs, the police would be involved ... how he got illegal drugs."

Matthew - who was laid to rest last week in a funeral attended by his co-stars Jennifer Aniston, Matt Le Blanc, David Schwimmer, Courteney Cox, and Lisa Kudrow- is believed to have drowned, but law enforcement sources told TMZ first responders were scrambled for a cardiac arrest.

The actor's assistant made a frantic 911 call after the actor appeared to have suffered a heart attack.

But the dispatch audio clip, which was only 15 seconds and has been obtained by TMZ, referred to a drowning by stating there was an 'Emergency Medical Situation 9'.

A first responder is heard saying: "Agent 23. Rescue 23. EMS 9 on the radio. In response to the drowning."