At least nine Americans killed in Mexican highway ambush

At least nine U.S. citizens, including six children, were killed Monday in an apparent ambush on a highway in the Mexican border state of Sonora, according to relatives of the victims and local media reports.

The dead included 8-month-old twins, said a family member, Kendra Lee Miller. Eight children survived, some seriously wounded, including a 9-month-old who was shot in the chest and a 4-year-old shot in the back, Miller said.

Willie Jessop, who is related to one victim, told NBC News by phone from Utah that the attack was on a motorcade consisting of several families, and that survivors at the scene told him that three cars were shot at and one was set on fire.

The Mexican government said Tuesday that three Chevy Suburban SUVs were hit in the assault.