Heath Ledger, who died January 22 in a New York apartment, suffered from an addiction to sleeping medication, a source close to the situation confirmed to MTV News.

Police have speculated that Ledger's death may have been caused by an accidental overdose, although initial autopsy results were inconclusive. The Associated Press reported last week that prescription pills, iincluding those for insomnia and anxiety, were found throughout Ledger's apartment. A full toxicology report is under way, the results from which should be known within a few weeks.

According a recent article on Us magazine's Web site, Ledger's ex-fiancee, Michelle Williams, strongly urged the 28-year-old star to enter Malibu, California's Promises Treatment Center, a rehab facility, in March 2006, just weeks after the pair were both honored with Oscar nominations for their work in "Brokeback Mountain."

Part of Ledger's reluctance to enter rehab in the months leading up to his death may have been a reluctance to "prove his ex right," the source told MTV News.

Ledger's family has responded to media speculation about Heath's death, asking that the world wait for the medical examiner to make a determination before jumping to conclusions. The family also denied Ledger was using drugs.

The confirmation comes a day after several syndicated entertainment shows, including "The Insider" and "Entertainment Tonight," quashed a video that reportedly showed Ledger talking about drugs at a Hollywood party. In the video, Ledger is seen reportedly saying, "I used to smoke five joints a day for 20 years." AP reports that Natalie Portman and Sarah Jessica Parker, among other celebrities, pressured "ET" not to run the video.

(Watch family and friends mourn Heath Ledger in New York on Friday, see him talk about his evolution as an actor in a 2005 interview with MTV News, and read his colleagues' and admirers' reactions about the tragic news right here.)

[This story was originally published at 3:27 p.m. ET on 01.31.08]