The investigation into where Heath Ledger obtained the two painkillers that contributed to his death has been dropped by US prosecutors.
A Drug Enforcement Agency inquiry had been taking place to find out if the drugs were acquired illegally.
But the prosecutors have bowed out "because they don't believe there's a viable target."
Prosecutors in the US attorney’s office in Manhattan have said there is no way they would be able to find out how the 28-year-old obtained oxycodone and hydrocodone, two of six drugs found in his system.
Actress Mary-Kate Olsen was the first person called when Ledger’s body was found – police believed she could provide information about the fatal drugs.
Olsen refused to speak to investigators earlier this week, unless she was granted immunity from prosecution.
The actress was subpoenaed to talk, but now the probe has been dropped that won’t be enforced.
Ledger was found dead in his Manhattan apartment on January 22, after an accidental overdose.