Nine people were killed in a car accident on an Arizona highway Wednesday night, the Associated Press reports. The Arizona Department of Public Safety said a vehicle collided head-on with an SUV carrying nine people on State Route 79, about 60 miles southeast of Phoenix. Investigators say they don’t know what caused the crash. The SUV’s driver, front-seat passenger, and five back-seat passengers were killed. Two others in the SUV were taken to local hospitals. The driver and the front-passenger of the other vehicle also died in the crash. Seven of the nine killed were undocumented immigrants, the AP reports.