Officials in northern Mexico say a tractor-trailer has collided with a bus carrying Canadian and American tourists, killing at least 11 passengers and the bus driver.

Eight U.S. citizens are among the dead and 11 other Americans are believed to be injured or hospitalized. Reports also say three Canadians were killed.

Authorities say the tourists were traveling south from the Texas border town of McAllen through the Mexican state of Coahuila when the accident happened Monday. It was not clear how many people were aboard the bus.

U.S. State Department spokesman Robert Wood Tuesday said local officials have confirmed the identities of four of the Americans killed but that their identities are being withheld pending notification of next of kin.

Wood also extended condolences to the families of those killed and injured. He said U.S. consular officials in Monterrey and Reynosa, Mexico, have been providing assistance.