Weezer [ tickets ] bassist Mikey Welsh has checked into a psychiatric hospital, and the group is currently auditioning temporary replacements for Weezer’s upcoming fall tour.

In a posting on Weezer’s official website, webmaster Karl Koch said the band still has little information regarding Welsh’s condition.

"We have learned that Mikey has checked into a psychiatric hospital, we think in his hometown of Boston," Koch wrote. "However, we unfortunately still don’t know what’s wrong with him, and continue to find it very difficult to find out any more from those who might know. We wish him the very best and we hope he comes back soon. But in the meantime, due to the circumstances at hand with the upcoming tours and such, we are indeed hastily scheduling try-outs for a replacement player for the upcoming gigs, JUST IN CASE Mikey isn't able to return."

Weezer first learned that something was amiss with Welsh when the bassist missed a red-eye flight from Boston to Los Angeles late Tuesday night, according to a posting to the website. Welsh was absent from Wednesday’s (8/15) taping of a second version of the "Island in the Sun" video, with Spike Jonze directing.

The band's fall tour with Cold is currently slated to begin on Sept. 11 in San Jose, Calif. However, a spokesperson for Weezer told liveDaily that the tour may be re-routed.

Weezer released a self-titled CD, known as "The Green Album" earlier this year, and is already writing songs towards a new LP. "The guys are learning new songs together in rehearsal, and they are up to 23 brand new (written within the last month) songs," Koch wrote.

Tentative dates for Weezer's upcoming tour with Cold follow: