Federal drug investigators are probing two doctors over the death of actor Heath Ledger, it has been learned.

The doctors – one in California, one in Texas – are believed to have supplied the “Brokeback Mountain” star with the powerful painkillers Oxycontin and Vicodin, law enforcement sources said. Authorities want to know if the drugs were prescribed illegally. “It’s an ongoing investigation,” a law enforcement source told The News Tuesday. “It’s not clear if there was any wrongdoing.”

The revelation came more than a month after the 28-year-old Australian heartthrob’s naked body was found in his SoHo loft.

The city’s medical examiner ruled Ledger died on Jan. 22 of an accidental overdose of six prescription drugs, including the two painkillers, sleeping pills and anti-anxiety medication. The federal Drug Enforcement Administration has subpoenaed the medical examiner’s findings as part of its probe into the doctors, the sources said.