Mary-Kate Olsen MKOlsen062608_03_X17a.jpg Archive photo

The NYPD may have left Mary-Kate Olsen alone in the wake of Heath Ledger's death earlier this year - but the DEA's coming full steam ahead for the pint-sized actress!

Access Hollywood reports that the Drug Enforcement Agency has issued a subpoena which would force Olsen to testify about her role in the events surrounding Ledger's tragic overdose in January.

Specifically, the feds plan to pump Olsen for information about how Ledger might have acquired certain prescription drugs found in his apartment without a prescription, including the powerful painkiller OxyContin.

The actress' role has been the subject of much debate since it was revealed that Heath's masseuse called Olsen before calling 911 after discovering the actor's body. To make things even more mysterious, recent reports claim that Olsen has refused to speak to the feds unless they guarantee her immunity from prosecution.

Yesterday, Olsen's lawyer told the media that "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."

Calls to the DEA spokesperson were not returned in time for publication.

Guess we'll see just how much Mary-Kate knows once she testifies - unless she starts pleading the fifth, of course!