Bill Cosby -- Vegas Casino Pulls the Plug on Concert

Bill Cosby's comedy tour is starting to crumble ... Vegas and another venue just cancelled concerts.

Cosby was slated to perform at Treasure Island in Las Vegas a week from today and at the Desert Diamond Casino in Tucson, Arizona February 15 ... but those shows have now been 86'd.

A rep for Treasure Island released a statement calling the decision "mutual." The casino will offer refunds. TMZ spoke with the casino just two days ago and there were no plans to cancel.

Cosby performed Thursday night in the Bahamas at a benefit for an African American women's service organization.

None of the other venues for his concert series have pulled the plug ... yet.

9:53 A.M. PST -- One more appearance -- at the Virginia Theatre in Champaign, IL -- just got cancelled for April.