SANTA YSABEL, Calif. -- Four people, including two children, were killed and five people injured Tuesday in a head-on collision west of Santa Ysabel.

A 33-year-old San Diego woman was driving a Honda Odyssey with a 67-year-old female passenger and six children in the back who ranged in age from 3 to 13, according to California Highway Patrol Officer Brian Pennings.

They were headed east on state Route 78 near the intersection with state Route 79 about 3:15 p.m. when the vehicle collided head-on with a 2010 Pontiac Vibe being driven west by a man whose name was not released, Pennings said.

Both drivers were killed along with an 8-year-old girl and a 9-year-old girl, Pennings said. They died at the scene, he said.

A 6-year-old girl sustained major, possibly life-threatening injuries and was hospitalized along with a 3-year-old boy, an 8-year-old boy and a 13-year-old girl who sustained moderate to minor injuries, Pennings said.

The van's front seat passenger, a San Diego woman and the vehicle's registered owner, was also taken to a hospital with major injuries, Pennings said.

Three of the injured were flown to a hospital and the others were taken by ambulance, according to Capt. Mike Mohler of Cal Fire.

Both eastbound and westbound State Route 78 were closed two miles west of State Route 79, according to the CHP.

The cause of the crash was still under investigation.