Four bicyclists participating in a group ride in West Marin on Saturday were struck and injured by a vehicle that fled the scene.

Authorities are seeking the public’s help in finding the driver of a midnight blue, crew cab Dodge Ram that is believed to have intentionally struck the bicyclists participating in the organized bike ride in which Marin County Bicycle Coalition is a beneficiary. About 1,300 bicyclists were registered to take part in the event leading cyclists from Stafford Lake to as far out as Sonoma County.

“That somebody can do this and drive off is inconceivable to me,” said Jim Elias, executive director of the Marin County Bicycle Coalition.

The four bicyclists were riding westbound on Point Reyes-Petaluma Road, just west of Hicks Valley Road, as part of the Jensie Gran Fondo of Marin, when they were struck from behind by the vehicle just before noon, said California Highway Patrol Officer Andrew Barclay.

Witnesses described the vehicle as intentionally swerving to the right to swipe the cyclists, he said.

The injuries suffered varied among the bicyclists, whose identities were not available Saturday afternoon. One cyclist who suffered “major injuries” was taken by helicopter to Santa Rosa Memorial Hospital. Three people with less severe injuries were taken by ambulance to Marin General Hospital.

Elias, who was at the scene shortly after it happened, said the most severely injured cyclist was thrown into a ditch after he was hit.

“His bike was destroyed worse than any bike I’ve seen destroyed from a crash,” he said. “It was a dramatic scene in that regard.”

The other cyclists were able to talk, Elias said, but one cyclist appeared to have suffered a concussion or other head injury and could not remember anything.

Elias said the cyclists were not riding in the road but were in a line, one behind another, to the right of the road.

Officials were seeking the slightly-lifted truck that is believed to be about 10 years old. The truck has black rims, wheels that “protrude out past the body of the truck,” and no front license plate. The truck is expected to have right-front damage, Barclay said.

The driver was described as a 20- to 35-year-old white male with stubble and a brown crew cut.

The promotion material for the Jensie Gran Fondo of Marin offered a “ProTour level experience,” traveling along “the world class roads of Marin County, with notable views of Alpine Dam, Mount Tam, Stinson Beach, Bolinas, Point Reyes and Tomales Bay.”

Anyone with information is encouraged to contact CHP at 707-551-4100.