A major wreck shut down a busy highway near Phoenix, Ariz., Friday. Authorities say the driver of the tour bus rear-ended a car and then rolled over.

Rescuers broke out windows on the bus to reach the victims. Six people on board were killed, and at least a dozen others were injured. The bus was traveling on Interstate 10 from Mexico to Los Angeles with 22 people on board.

In a separate accident in Wisconsin, 20 cars piled up near Highway 55 near Kaukauna. No one was seriously injured in the accident.

It's believed thick fog brought visibility in the area down to zero.