As the investigation surrounding Heath Ledger’s accidental overdose continues, the federal Drug Enforcement Administration office in New York has confirmed to “Access Hollywood” that they have issued a subpoena that would force Mary-Kate Olsen to testify in front of a grand jury.

Five medications were found in Ledger’s body at the time of his death, according to the DEA, three of which he’d obtained via doctors in Texas and Los Angeles. At the center of the investigation is how he acquired Oxycontin and Vicodin without a legal prescription.

Olsen was the first person called by the masseuse who discovered Ledger’s body after the “The Dark Knight” actor’s untimely death.

She broke her silence for the first time on Monday, when a rep for the actress told “Access” in a statement that she “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.”

However, despite the rep’s statement that they “have provided the government with relevant information,” the actress is reportedly refusing to speak to government officials without immunity.

According to Benjamin Brafman, a high-profile defense attorney not associated with the case, seeking immunity is not the same as admitting guilt.

“It may not mean anything other than she’s getting good legal advice,” Brafman told “Access.”

“You don’t know what the DEA may suspect in this case and I think it’s a cautious way to proceed. I think it would be wrong to assume she’s done something criminal simply because she’s invoking her Fifth Amendment against self-incrimination.”

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