CIUDAD VICTORIA, Mexico (AP) — A bus carrying patients for treatment of chronic illnesses flipped in northern Mexico near the U.S. border Tuesday, killing 12 people and leaving 10 others injured. 

The bus had been rented by the Mexican Social Security Institute in the city of Matamoros, across the border from Brownsville, Texas. The patients and their relatives were being taken to a hospital in the neighboring state of Nuevo Leon for specialized treatment when the accident occurred.

Pedro Granados Ramirez, the head of the Tamaulipas state civil defense office, said the accident occurred on a curve near a border bridge in the city of Reynosa. Nine people, including the driver of the bus, died at the scene and three more at a hospital. 

The condition of the 10 injured passengers ranged from stable to serious.