Washington, Feb 7 : Now that it has been proved that Heath Ledger died of an overdose of prescription pills, the federal government is stepping in to investigating how the actor was able to obtain so many drugs.

New York's Drug Enforcement Administration spokesman Erin Mulvey confirmed that they would investigate how the actor obtained the various drugs.

"We are working with the NYPD to identify any illegally prescribed drugs that may have been prescribed to [Ledger]," People quoted Mulvey, as saying.

The New York City medical examiner's office ruled that Ledger died due to an accidental overdose of a deadly cocktail of prescription drugs.

Ellen Borakove, a spokeswoman for the office, said that the cause of death was 'acute intoxication by the combined effects of six different drugs including Oxycodone, Hydrocodone, Diazepam, Temazepam, Alprazolam, and Doxylamine.

ANI