A three-vehicle crash on southbound Highway 101 at Hopper Avenue in Santa Rosa on Saturday morning closed the two left lanes of the freeway and sent two people to the hospital, the CHP said.

A big rig towing a flat-bed trailer jackknifed on the freeway after sideswiping a Jeep Cherokee that merged into the southbound lanes from the Hopper Avenue on-ramp shortly after 10 a.m., the CHP said.

A Honda Civic behind the big rig then collided with the cab of the truck after it came to a stop along the median.

The Jeep's driver and passenger were taken by ambulance to Memorial Hospital with undisclosed injuries, authorities said.

The lanes reopened at 11:26 a.m., according to the CHP.

The chain-reaction collision began after the Jeep was sideswiped by the big rig and spun out, causing the truck to jackknife and come to a stop with its cab along the median and its trailer blocking the inside two lanes of the freeway.

The Honda, driven by Terry Wong of Windsor, swerved to avoid the trailer and wound up hitting the cab of the truck.

"I didn't know what to do," said Wong, whose 7-year-old was in the car. "It was a split-second reaction. You've got to make up your mind."

Wong was sore, but he said he and his son were otherwise uninjured in the collision.

The big rig driver, Martin Lupercio of Red Bluff, had just delivered a load of rocks in Fulton and his trailer was empty when he saw the Jeep try to merge in front of him.

"I tried to brake, but it was too close," said Lupercio, who was uninjured. "I tried to stop; then I went out and hit the wall."

The crash backed up southbound traffic significantly.

(You can reach Staff Writer Matt Brown at 521-5206 or matt.brown@pressdemocrat.com.)