Tests were required to establish the identity because the body, discovered Friday, had started to decompose. The cause of death had not been determined, a representative of the King County Medical Examiner's office said Saturday without giving his name.
Police did not immediately release details on anything that was found at the scene, and a spokesman did not respond to several messages.
With Nirvana, Pearl Jam and Soundgarden, Alice in Chains was one of the most prominent bands of the Seattle grunge scene of the early '90s. The group was known for its dark, menacing sound, which combined grunge and heavy metal, and often wrote about heroin.
In a 1996 interview with Rolling Stone magazine, Staley spoke of how his drug use influenced his lyrics.
"I wrote about drugs, and I didn't think I was being unsafe or careless by writing about them," he told the magazine. "Here's how my thinking pattern went: When I tried drugs, they were (expletive) great, and they worked for me for years, and now they're turning against me — and now I'm walking through hell, and this s--ks."
The group's first album, "Facelift," was released in 1990. It later released "Dirt" and "Alice in Chains." The group's hits included "Man in the Box," "Them Bones," "Rooster," and "Would?"
The latter song was about Andrew Wood, singer of the seminal grunge group Mother Love Bone. Wood died of heroin overdose in 1990.
Staley's body was found just over 8 years after Nirvana singer and guitarist Kurt Cobain was found dead in his Seattle home of a self-inflicted gunshot wound. Heroin was found in Cobain's bloodstream, and his head had been so mutilated that he could not be immediately identified.