A driver who slammed into a group of motorcycle riders, killing four of them and his companion, has been arrested on suspicion of driving under the influence, and police are looking for another driver who may have triggered the crash.

The motorcyclists were riding Saturday to celebrate the 10th anniversary of their club when a driver in a gold Honda Civic passed them on a two-lane highway 80 miles (130 kilometers) east of San Diego. California Highway Patrol officer Deann Goudie said that maneuver forced an oncoming car off the road and then it veered back on and into the group.

She said authorities were looking for the Honda, which has California plates.

None of the motorcyclists got the license plate number of the Honda driver - described as a man wearing a baseball cap - and none of them pursued him, choosing to stay behind to help their friends.

"I was the first person on scene that had a uniform on," Goudie said Sunday. "I was being dragged in every direction by frantic people saying, 'Help this person, help that person.'"

Goudie said investigators on Monday would check surveillance video at a nearby border crossing to see if the driver went to Mexico.

Carlos Ramirez Bobadilla, 36, was arrested when officers smelled alcohol on his breath about five hours after the crash, Goudie said.

Ramirez, one of six injured in the collision, was recovering from hand fractures at a San Diego hospital, Goudie said.

It was unclear if the driver's alleged alcohol consumption contributed to the collision, Goudie said, but he was arrested on a misdemeanor and is not being held responsible for the deaths based on evidence collected so far. Results of a blood test were pending and not expected for about two weeks, she said.

Ramirez, of Mexicali, Mexico, swerved his white Dodge Avenger to the right shoulder of state Route 98 to avoid the Honda and then overcompensated by swinging left into oncoming traffic, Goudie said. Ramirez's speedometer was found stuck at 60 mph (100 kph), 5 mph (8 kph) below the speed limit.

The CHP withheld names of the five who died, pending notification of next of kin. They included a husband and wife who were on a motorcycle that was first to be struck.

Carl Smith, president of the Lakeside-based Saddletramps Motorcycle Club, said three riders were seriously injured but expected to survive. Two others had less serious injuries.

Source: Elliot Spagat from Associate Press.