He was 48.
His manager, Tom Vitorino, confirmed his death, but he didn't disclose the cause.
Weiland was on tour with the band, The Wildabouts. Cocaine was found in his tour bus bedroom near his body, the Bloomington, Minnesota, police department said.
Another band member, Tommy Black, was arrested on suspicion of fifth-degree possession of a controlled substance, but has not been formally charged, police said. Authorities said cocaine was found in the area of the bus occupied by Black.
Deputy Chief Denis Otterness told CNN that authorities don't believe Weiland's death is connected to Black's possession case.
"There was nothing that appeared suspicious at the scene, and no evidence of foul play," he said.
In addition to the small quantity of cocaine discovered, police collected other evidence, but their news release didn't describe those items.
"Scott Weiland, best known as the lead singer for Stone Temple Pilots and Velvet Revolver, passed away in his sleep while on a tour stop in Bloomington, Minnesota, with his band The Wildabouts," a statement on his Facebook page said
. "At this time we ask that the privacy of Scott's family be respected."
His old band also posted a statement.
"Let us start by saying thank you for sharing your life with us," Stone Temple Pilots members Dean DeLeo, Robert DeLeo and Eric Kretz wrote. 'Together we crafted a legacy of music that has given so many people happiness and great memories. The memories are many, and they run deep for us."
They continued, "You were gifted beyond words, Scott. Part of that gift was part of your curse. With deep sorrow for you and your family, we are saddened to see you go. All of our love and respect. We will miss you brother."
A powerful baritone
The Stone Temple Pilots came on the scene at the height of the grunge movement, releasing its first album, "Core," in 1992. Critics were unkind, accusing them of being poseurs riding the coattails of Nirvana and Pearl Jam.
But it didn't matter. "Core" and its 1994 follow-up, "Purple," sold more than 10 million copies. STP won a Grammy in 1994 for the song "Plush" and had monster hits with "Vasoline" and "Interstate Love Song."
A big part of its success was Weiland's powerful baritone that he effortlessly contorted into a raspy growl when needed. A flamboyant personality helped, which he played to the hilt during live shows.
But his drug addiction didn't.
He missed shows repeatedly. He would go into rehab and then relapse. The band had all the trappings of success -- headlining tours, appearances on "Saturday Night Live," platinum sales -- but an unstable frontman.
In 1995, Weiland was arrested in Pasadena, California, and charged with possession of heroin and cocaine. His wife posted bond and was driving him home when he leaped out of their moving car and went to his dealer's house.
Stone Temple Pilots was forced to go on hiatus after the release of its 1996 album, "Tiny Music ... Songs from the Vatican Gift Shop," which sold 2 million copies and was widely praised.
The band minced no words as to why.
Weiland, it said in a statement, "has become unable to rehearse or appear for these shows due to his dependency on drugs. He is currently under a doctor's care in a medical facility."
In a 1997 Rolling Stone interview, Weiland acknowledged his addiction problems.
"It got to the point where I didn't feel like I got a good enough rush unless I had one hand on the needle and one hand dialing 911," he told the magazine
He was apparently enjoying sobriety at the time -- the magazine said he'd been clean for six months -- but it didn't last. He later served time in jail for violating probation
in a 1998 heroin conviction.
"Basically, your honor, Mr. Weiland is on the road to killing himself," said Los Angeles County Deputy District Attorney Norm Montrose at the sentencing.
Stone Temple Pilots stuttered on through two more albums, but the audience had moved on. It finally disbanded in 2003.
Sure, there were short reunions, and everybody said all the right things.
"I think of some of the tours we were on, and they were a little rambunctious," Weiland told CNN in 2011, three years after a huge reunion tour.
"What we did onstage was kind of what it was like all the time," added bassist Robert DeLeo.
But the friction was still there, and Weiland kept getting fired.
He bounced back, at least professionally.
He joined Velvet Revolver formed by former Guns N' Roses members who'd had enough of Axl Rose.
Weiland delivered hits for them, for sure. The debut album, "Contraband," sold more than 3 million copies and yielded a massive hit, "Slither," and another Grammy for Weiland.
Dogged by drugs
But the drug addiction dogged him.
"Sometimes there's certain people who've just gone too far and you can't fix it," bassist Duff McKagan said in one interview.
In between were arrests, several of them. Aside from the 1995 crack cocaine arrest, there was a DUI in 2003, another DUI in 2007.
He released several solo albums, formed several bands and wrote a memoir, "Not Dead & Not for Sale," that was published in 2011. The memoir included stories of being raped when he was 12
and his relapses, including "a single line of coke" that doomed his future with Velvet Revolver.
He recorded a Christmas album and crooned "The Christmas Song" and "Winter Wonderland."
He talked about reuniting with both Stone Temple Pilots and Velvet Revolver.
Those dreams ended on a tour bus in Minnesota, where he was found dead.