Carrie Fisher's autopsy report shows the actress had cocaine, ecstasy and heroin in her system at the time of her death.
But investigators could not determine what impact the cocktail of drugs found in her system had on her death.
The report, released on Monday, states Fisher may have taken cocaine three days before the December 23 flight on which she became ill. She died four days later, aged 60.
"The exposure to cocaine took place sometime approximately in the last 72 hours of the sample that was obtained," stated the report.
It also found traces of heroin and MDMA, which is also known as ecstasy, but that they could not determine when Fisher had taken those drugs.
"Based on the available toxicological information, we cannot establish the significance of the multiple substances that were detected in Ms Fisher's blood and tissue, with regard to the cause of death," the report said.
The findings were based on toxicology screenings done on samples taken when the Star Wars actress arrived at a Los Angeles hospital.
Coroner's officials ruled Fisher died from sleep apnoea and a combination of other factors.
The coroner also said Fisher suffered from atherosclerotic heart disease and "drug use," but no specifics were given at the time.
"The manner of death has been ruled undetermined," the report concluded.
Fisher's daughter, Billie Lourd, addressed the report in a statement to People magazine.
"My mum battled drug addiction and mental illness her entire life. She ultimately died of it," she said.
"She was purposefully open in all of her work about the social stigmas surrounding these diseases. She talked about the shame that torments people and their families confronted by these diseases.
"I know my Mum, she'd want her death to encourage people to be open about their struggles. Seek help, fight for government funding for mental health programs. Shame and those social stigmas are the enemies of progress to solutions and ultimately a cure. Love you Momby."
Fisher's brother, Todd Fisher said he was not surprised that drugs may have contributed to his sister's death.
"I would tell you, from my perspective that there's certainly no news that Carrie did drugs," Todd Fisher said. He noted that his sister wrote extensively about her drug use, and that many of the drugs she took were prescribed by doctors to try to treat her mental health conditions.
Fisher long battled drug addiction and mental illness. She said she smoked pot at 13, used LSD by 21 and was diagnosed with bipolar disorder at 24. She was treated with electroshock therapy and medication.
"I am not shocked that part of her health was affected by drugs," Todd Fisher said.
He said his sister's heart condition was probably worsened by her smoking habit, as well as the medications she took. "If you want to know what killed her, it's all of it," he said.
- additional reporting by AP