US prosecutors have dropped a criminal investigation into where Heath Ledger got the powerful painkillers that led to his overdose death.
The US Attorney's office was working with the Drug Enforcement Administration (DEA) in an inquiry to find out whether the painkillers found in Ledger's system were obtained illegally.
But prosecutors have now decided not to pursue the case because they "don't believe there's a viable target", an official said today.
The decision followed reports that actress Mary-Kate Olsen was demanding immunity before answering any questions about Ledger's death and his drug use.
Authorities say Olsen, who was rumoured to be romantically linked to Ledger, was the first person called by a masseuse who found the 28-year-old Dark Knight actor's lifeless body in the Manhattan apartment he was renting from the famous twin.
The DEA had obtained a subpoena that could have forced Olsen if she continued to hold out. But the subpoena, issued in April, is no longer valid because it was contingent upon prosecutors pursuing the case, the official said today. But the case could still be revived if evidence of a crime emerges.
Rebekah Carmichael, a spokeswoman for the US Attorney's office, said it's the office's policy to "neither confirm nor deny the existence of an investigation". There was no immediate response to a message left for Olsen's lawyer, Michael C Miller.
DEA investigators suspect the painkillers found in Ledger's system, oxycodone and hydrocodone, were obtained with phony prescriptions or other illegal means. Oxycodone is sold as OxyContin and hydrocodone as Vicodin.
Miller insisted this week that Olsen, a former child star on the TV sitcom Full House, had already told the government she "does not know the source of the drugs Mr Ledger consumed".
