THOUSAND PALMS, Calif. -

A 9-month-old girl was killed on Sunday evening in an accident on Interstate 10 involving three cars.

A California Highway Patrol spokesperson said the collisions happened around 6:45 p.m. in the westbound lanes, just east of the Monterrey Avenue exit.

Witnesses said a 1997 Saturn SL4, driven by Alyissa Gross, 21, of Coachella, tried to enter the flow of traffic from the lane closest to the center divide when the car was hit from behind by a 2005 Ford F-150, which was traveling at approximately 70 mph.

The impact sent the Saturn, carrying Gross, another woman and three small children, crossing lanes of the freeway, colliding into another Ford F-150 truck, which hit the guardrail. The Saturn came to rest on the north shoulder near the 2005 Ford F-150, the spokesperson said.

All of the occupants of the Saturn were taken to Eisenhower Medical Center for treatment of major injuries. Nine-month-old Naveah Sessoms later died at the hospital.

CHP investigators determined her child safety seat was not properly secured, resulting in her death.

The drivers of both Ford F-150s were not injured.

CHP investigators are still trying to determine why the Saturn was entering the freeway from the center median.

They reminded drivers who need to pull over to the side of the freeway to use the right-hand side.