Heath Ledger Investigation Reportedly Closed; Mary-Kate Olsen Won't Have To Testify

U.S. Attorney's Office filed no charges before closing probe into actor's overdose death.

The investigation into Heath Ledger's accidental death by drug overdose has been closed by the U.S. Attorney's Office, which will not seek to enforce a subpoena against actress Mary-Kate Olsen that would have compelled her to testify in front of a federal grand jury, a source told People.com.

Olsen was the first person Ledger's housekeeper called after "The Dark Knight" star was found dead in his New York apartment January 22, killed by a lethal drug cocktail that included painkillers Oxycontin and Vicodin. Because the prescriptions could not be traced, the Drug Enforcement Administration had been interested in discovering how the actor secured such powerful narcotics.

On Monday, a lawyer representing Olsen issued a statement claiming the 22-year-old former "Full House" actress had no knowledge that could be of any help in determining how Ledger obtained the drugs.

"Despite tabloid speculation, Mary-Kate Olsen had nothing whatsoever to do with the drugs found in Heath Ledger's home or his body, and she does not know where he obtained them," attorney Michael C. Miller told People in a statement.

According to People, the investigation into Olsen was closed without any charges being filed.

Earlier this year, federal agents similarly cleared two doctors of any wrongdoing in connection to the drugs, which were deemed not to have come from either source.

With the two doctors and Olsen cleared, it remains unknown at this time how the actor secured the medication. In addition to Oxycontin and Vicodin, Ledger's autopsy also found the presence of Xanax, Valium, Temazepam and Doxylamine.

Ledger is currently getting universal acclaim for his performance as the Joker in "The Dark Knight."