The New York City medical examiner has found the cause of actor Heathcliff Ledger’s death to be “acute intoxication” from a mix of prescription painkillers and anti-anxiety medication.

Six bottles of pills had been found in the 28-year-old Oscar winner’s bedroom and medicine cabinet, but the cause of death took two weeks to determine after an initial autopsy the day following his death yielded no results.

The medical examiner said in its ruling that a combination of oxycodone, hydrocodone, diazepam, temazepam, alprazolam, and doxylamine had been found in a series of blood and tissue tests. Oxycodone, found in Oxycontin, and hydrocodone, found in Vicodin, are painkillers. Diazepam, temazepam, and alprazolam are anti-anxiety drugs found in Valium, Xanax, and Restoril.

The manufacturers of two brand-name opioid analgesics, Purdue Pharma L.P., which makes Oxycontin, and Abbott Laboratories, which makes Vicodin, publish patient information on their Web sites warning that misuse can lead to addiction or fatal overdose.

The medical examiner and police did not disclose whether Ledger had taken generic or brand-name versions of the drugs.

“We have concluded that the manner of death is accident, resulting from the abuse of prescription medications,” the medical examiner, Charles Hirsch, said in a statement.

Ledger, who played a cowboy in “Brokeback Mountain” and the Joker in the upcoming Batman movie, was found lying facedown and naked in his bed in a SoHo apartment on the afternoon of January 22.

A masseuse — who discovered the body when she arrived for an appointment — and Ledger’s housekeeper tried to revive him. They eventually called 911 after making phone calls to Ledger’s friend, the actress Mary-Kate Olsen.

The mystery surrounding the high-profile death prompted widespread speculation, although police determined early on that the death was not a homicide.

In the end, Ledger’s death appeared to be part of what has become a growing trend of accidental deaths linked to the abuse of prescription drugs, particularly opioid analgesics such as oxycodone and hydrocodone.

A study by Centers for Disease Control researchers published in 2006 showed that between 1999 and 2002, the number of unintended deaths related to opioid analgesics rose 91%, outstripping the combined number of deaths related to heroin and cocaine.

A statement by Ledger’s father, Kim Ledger, released yesterday said his son’s death “serves as a caution to the hidden dangers of combining prescription medication.”

“While no medications were taken in excess, we learned today the combination of doctor-prescribed drugs proved lethal for our boy,” he said in the statement.