The heavy metal rocker was found dead in a Woodland Hills, CA hotel room in August, but police were unsure what had killed him at the time.
An initial autopsy proved inconclusive, leading coroners to run a full toxicology report on the late musician.
The newly-released report determined that Lane died from alcohol poisoning, according to City News Service.
Lane had been arrested twice on DUI charges in the last several years of his life and was sentenced to 120 days in jail in July 2010.
Several heavy metal stars paid tribute to Lane following his death, including Poison frontman Bret Michaels.
Michaels tweeted: "We'd like to offer our deepest condolences to the family of Jani Lane regarding their loss. Respectfully, Bret and all at MEG."
Twisted Sister's Dee Snider wrote: "Jani Lane's is yet another sad story of a boy who attained his dreams of greatness, only to be blindsided by the pressures, temptations and disappointments of those same dreams.
"We all watched over the years, as he soared, stumbled, fell, then got up again and again. Tragically, he will get up no more. RIP Jani."
Lane was survived by his two daughters Taylar and Madison.
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