COTTONWOOD, Calif. -

A CHP truck was one of four vehicles involved in a chain reaction crash that tied up traffic on Interstate 5 in Tehama County Wednesday morning.

Southbound traffic was reduced to one lane in the Cottonwood area, just south of Redding.

The collision happened just after 6:30 a.m. Wednesday.

Officers said a yellow vehicle was northbound when it crossed the center divide and into oncoming traffic.  The yellow vehicle struck another car.

The driver of a Nissan pickup truck tried to avoid the initial crash, but collided with a CHP truck.

Four people suffered moderate to minor injuries.

As of 9 a.m., southbound traffic remained reduced to one lane.