Traffic snarled on Lakeville Highway in Sonoma County Thursday after a northbound Dodge pickup apparently swerved into an oncoming lane, causing chain reaction crashes involving about seven cars, CHP officials said.

Several people were injured including the driver of the Dodge, a 41-year-old man from Coulterville who fled the crash scene and was apprehended later, Officer Mike Phennicie said.

The man, whose name wasn't immediately available, was being treated at Santa Rosa Memorial Hospital for head injuries and will be arrested on an outstanding warrant, Phennicie said.

The crash began moments before noon on Lakeville Highway about a quarter mile north of Highway 37.

"It happened so fast, I saw a white truck swerving into our lane, next thing you know ... I ended up getting ripped, knocked off the road," said Byron Byers, 34, of Laytonville who was heading south to see family in Hollister.

Five vehicles ahead of Byers swerved to miss the Dodge, some getting clipped and all ending up in a ditch off the side of the road.

The Dodge clipped his Pontiac and he careened off the road, crumpling the front end as it crashed into a barbed-wire fence, said Byers, who suffered bruises and cuts.

In the seventh southbound car, Jack Chow, 43, of American Canyon was rear-ended as he tried to avoid a collision.

Chow, a San Francisco firefighter, got out and went to the Dodge to help a passenger trapped inside.

Chow helped peel back a window as the passenger climbed out.

"He brushed me off, then the guy in front, the driver, said, 'We gotta go, we gotta get out of here,'" said Chow.

CHP officials said family of the Dodge driver had been following in a Kia sedan, and the two men ran across the road, jumped into the Kia and the female driver sped off.

But witnesses noted the license plate and officers pulled the Kia over about ten miles north on Lakeville Highway near the northbound Highway 101 on-ramp, Phennicie said.

Two women, a driver and passenger, were in the front with the Dodge driver and his 18-year-old passenger in the back, he said.

All four were under investigation for their roles in the collisions and for fleeing the scene, Phennicie said.