Olsen Issued Subpoena in Ledger Investigation

Actress Mary-Kate Olsen, who once starred on the television show "Full House," has been issued a subpoena by the Drug Enforcement Administration office that will require her testimony in front of a grand jury in the investigation into the death of actor Heath Ledger.

Olsen, who has denied any involvement in Ledger's accidental overdose, originally said she would only speak with authorities if granted imunity from prosecution.

Ledger, who most recently played the Joker in the latest Batman installment of " The Dark Knight," had five diffrent medications in his system when he was discovered in his apartment in New York City. Three of the drugs he had reportedly received from doctors in Texas and Los Angeles. Officials are trying to determine how he obtained the OxyContin and Vicodin discovered in his apartment without a legal prescription.

Olsen, who was in California at the time of his death, was the first person that Ledger's housekeeper called after his masseuse found the actor dead on Jan. 22.