Sources: Olsen won't talk in Ledger probe

New York -- U.S. actress Mary-Kate Olsen reportedly isn't cooperating with an investigation into Heath Ledger's death unless she is granted immunity from prosecution

Australian film star Ledger died of an accidental prescription drug overdose in January. He was 28.

Olsen's masseuse reportedly called her before dialing 911 to request help for Ledger, whom the masseuse is said to have found unresponsive at his Manhattan home.

The New York Post said Olsen's attorney, Michael Miller, has repeatedly declined to allow federal investigators to question Olsen. The newspaper cited unnamed sources as saying federal officials may be forced to get a grand jury subpoena ordering Olsen to reveal what she knows about Ledger's behavior and what happened the day he died.

One insider told The Post, "Everyone has been very eager to help, saying what a great guy Heath Ledger was, everyone except Mary-Kate, who has refused to speak."

The source said Olsen would be the last witness investigators need to wrap up their investigation into how and where Ledger obtained drugs and medicines.

Olsen's lawyer had little to say when contacted by the newspaper, other than, "We are not going to comment on whether there is a criminal investigation."

Copyright 2008 by United Press International.