ANTIOCH, Calif. -- The search for a motorcyclist who fell off the Antioch Bridge following a collision Sunday evening has been called off, authorities said.



The search was officially halted around 6:30 p.m., U.S. Coast Guard Lt. j.g. Leigh Van Lear said.



After two hours of searching, emergency personnel were not able to locate the body, Contra Costa County Fire Marshal Robert Marshall said.



"They found some of his gear, they think," Marshall said. "There's no way to tie it to the rider himself, but they did find some belongings."



Marshall said the setting sun was a crucial factor in calling off the search.



"It was starting to get dark and it would have been dangerous to continue, so they had to get off the water," Marshall said.



He said crews are expected to resume looking in the morning.



California Highway Patrol officers responded around 4:30 p.m. to a report of a motorcycle speeding on the bridge, Officer Peter van Eckhardt said.



Soon after, van Eckhardt said officers received a report of a collision on the bridge.



Medical crews arrived on scene and Marshall said they found the motorcycle but no driver.



The motorcyclist was traveling south when the driver collided with a car and then "flew" over the west side of the bridge, Marshall said.



The involved car remained on scene and Marshall said no one inside the car was injured.



A Coast Guard rescue boat, the Contra Costa County sheriff's rescue boat, a CHP helicopter, the Contra Costa County Fire Protection District rescue boat, Oakley police and Rio Vista police all responded to the scene.



A Sig-alert, issued around 5 p.m. for both the southbound and northbound lanes, was lifted around 7:15 p.m.