Autopsy results in the death of 28-year-old actor Heath Ledger indicated the actor died of an accidental overdose of prescription medication.

Now, the federal Drug Enforcement Agency wants to know who prescribed the medications that killed Ledger, if the prescriptions were legal and how much the doctors responsible knew about the total medications Ledger was taking.

Ledger was discovered in his New York apartment on January 22nd, setting into motion a media firestorm of speculation and accusation on the actor’s apparent drug use.

Autopsy results, however, found no illegal drugs, instead ruling the young actor died of a lethal combination of prescription and over-the-counter drugs, including Xanax, Valum, temazepam (anti-anxiety drug) and doxylamine (a sleeping aid).

The federal Drug Enforcement Agency (DEA) is now investigating two doctors who reportedly were involved in prescribing drugs to Ledger, according to E! Online.

The two doctors, who have not yet been named, operate from California and Texas, respectively.

Authorities want to know if all the drugs Ledger was consuming were legally prescribed and whether the actor sought out multiple doctors to acquire more medications than one doctor could prescribe under federal law.

Ledger was found lying face down, naked and unresponsive in his bedroom by a housekeeper and a masseuse on January 22nd.

Though initial reports suggested Ledger may have attempted suicide, New York Police Department investigators quickly confirmed they found no evidence of foul play or that the actor committed suicide.

Ledger is survived by his two-year-old daughter Matilda with ex-fiancee Michelle Williams.