Mary-Kate Olsen can breathe a sigh of relief – The official investigation into the death of Heath Ledger has been closed because of a lack of evidence.

It was previously reported that The Wackness actress had been subpoenaed to testify in front of a grand jury as part of a probe into the mystery surrounding the late star's death.

Ledger died of an accidental prescription drugs overdose at his New York apartment in January.

Since the medications could not be traced, the U.S. Drug Enforcement Administration had been interested in learning how Ledger acquired such powerful substances.

Olsen's name was dragged into the case because the masseuse who found Ledger dead called the former child star before contacting the emergency services, prompting suspicion.

But now it looks as if the 22-year-old actress will escape having to give testimony after an unidentified official reportedly told People that prosecutors have closed the investigation "because they don't believe there's a viable target".