Thirteen people died Sunday morning after a tour bus slammed into the back of a big rig on Interstate 10 near Palm Springs while returning to Los Angeles from a casino near the Salton Sea. The Riverside County Coroner's office identified 11 of the victims Monday morning. Thirty one others were injured in the predawn crash, which shut down the westbound side of the freeway at Indian Canyon Drive, according to the California Highway Patrol. They were believed to be sleeping when the bus collided with the tractor-trailer truck shortly after 5 a.m., CHP Chief Jim Abele said at a news conference Sunday.