Mikey Welsh, the former bassist for the band Weezer, was found dead in his Chicago hotel room on Saturday.

The death of 40-year-old Welsh was unexpected and the cause was not immediately known, CNN reported, as toxicology tests are pending.

Chicago police spokesman Darryl Baety said police officials responded to a call from the Raffaello Hotel at 1:45 p.m. on Saturday about a guest who was due to check out, but hadn't.

Police found a person unresponsive and not breathing and are conducting an investigation for the cause of death with pending autopsy results. According to ABC News, police do not suspect foul play leading to the death of Welsh, though they suspect an overdose of narcotics was the cause while toxicology results pend.

Welsh was in Chicago with plans to attend Weezer's show at RIOTfest on Sunday night, according to Weezer.

Mikey Welsh, a Burlington, Vt. native, was a former member of Weezer from 1998 until 2001, when he left the band after suffering from a nervous breakdown stemming from drug use. In an interview with Rock Plum Salt in 2007, Welsh detailed his past drug usage, attempts at suicide and an overdose which lead him to seek out psychiatric help in 2001.

Basically, a lifetime of doing drugs and being undiagnosed as having disorder, post-traumatic stress disorder, and borderline personality disorder finally caught up with me when I was 30 years old, Welsh told Rock Plum Salt. At the beginning of a 3-month European tour with Weezer, I started slowly falling apart. Without getting too graphic, by the time the tour was winding up, my weight had gone down to about 140lbs (I'm 6'2) [63,5 kg - 1,85 m] and mentally completely wiped out. When I returned to the States, my family had made plans for me to see a psychiatrist in Boston. First though, we had to play a few dates around the U.S., and perform on The Tonite (sic) Show (which ended up being my last performance with Weezer). By the time I got to Boston, I was having a complete nervous breakdown. It ended with a severe suicide attempt (an overdose). I was found and rushed to the hospital where I had come to within minutes of my heart completely stopping. I was in a coma for a few days, and woke up in a lockdown psychiatric ward.

Karl Koch of Weezer posted a statement to the band's Web site expressing pain from the loss of their former bassist.

It saddens me and the guys in Weezer so much to say that our beautiful, creative, hilarious and sweet friend Mikey Welsh has passed away at the very young age of 40, Koch wrote. A unique talent, a deeply loving friend and father, and a great artist is gone, but we will never forget him. His chapter in the weezer story ('98 - '01) was vital, essential, wild, and amazing. We will miss him terribly. Our deepest heartfelt condolences go out to his family and friends. The world has lost a truly one of a kind guy.

According to Koch, Mikey Welsh has established a second career in painting for himself after leaving Weezer a glorious flowering of a talent he always possessed, according to Koch.