The US Attorney?s Office official investigation into Heath Ledger?s death has been closed without any charges being filed.

After Ledger ? who had a two-year-old daughter with former fiancee Michelle Williams ? died of accidental prescription drugs overdose in January, officials wanted to determine where he had obtained powerful painkillers Oxycontin and Vicodin ? two drugs for which he had no prescription.

Despite reports Ledger?s close friend Mary-Kate Olsen ? who was subpoenaed by a federal grand jury on 23 April ? would be forced to involve herself in the investigation, the probe has now been closed without the subpoena being enforced.

When Olsen ? who was the first person Ledger?s masseuse called after she found him dead in his New York apartment ? was issued with the subpoena, her attorney began negotiating with authorities, and was said to be trying to get the 22-year-old star immunity from prosecution before she would testify in the case.

He released a statement saying: ?Ms. Olsen had nothing to do with any drugs found and has already provided relevant information for the investigation.?

A coroner?s report showed Ledger died of an accidental overdose of prescription drugs for pain, anxiety and sleep.