(CNN) -- The death of actor Jeff Conaway was ruled accidental by the Los Angeles County Coroner's Office on Monday.
Conaway, who was in the TV series "Taxi" and the movie "Grease," died May 27 after being found unresponsive 17 days earlier, his manager said.
The accidental death came as a result of the drugs found in his urine when he was admitted to the hospital on May 10, according to the report.
It also stated that it is not known how long Conaway's brain was without oxygen before the actor was taken to the hospital, and that he "may have aspirated on his own vomit."
Pneumonia was initially ruled the cause of death, and the doctor who treated him for drug addiction for years said his dependence on prescription painkillers eventually cost him his life.
"Jeff was a severe, severe opiate addict with chronic pain, one of the most serious and dangerous combination of problems you could possibly interact with," Dr. Drew Pinsky, an addiction medicine specialist, said during a taping for a May "Dr. Drew" show on HLN.
"The pain seemed to be motivating him back to the opiates, and I told him for years that it was going to kill him," Pinsky said.
In the weeks before his death, Conaway, 60, suffered from pneumonia and sepsis. He was in a medically induced coma in an Encino, California, hospital for two weeks, manager Phil Brock said.
His family surrounded Conaway in his hospital room on May 26 when he was taken off life support, Brock said.
Conaway's struggle with alcohol and drug addiction was chronicled in 2008 on the TV reality show "Celebrity Rehab With Dr. Drew."
"What happens is, like with most opiate addicts, eventually they take a little too much, not much more than usual, and they aspirate, so what's in their mouth gets into their lungs," Pinsky said. "That causes a rapidly progressing and overwhelming pneumonia that they usually don't know that they have, because they're sort of too out of it because of the drugs. And by the time they get to the hospital, it's too late. That's what happened with Jeff."
There was no evidence he ever intentionally overdosed, Pinsky said.
Rachel Wells contributed to this report.