HAYWARD (CBS SF/BCN) — A motorcyclist died early Saturday when his bike hit the rear of a truck that was part of a slow-moving caravan of Caltrans vehicles street sweeping I-880 in Hayward, according to the California Highway Patrol.

CHP Officer Dustin Kennerley said four or five CalTrans trucks were traveling about five miles per hour as they swept debris from the center divide and left lane just north of the Mowry Avenue exit.

READ MORE: 'No Sideshow Zone;' Antioch Unveils Prevention, Enforcement Action Against Planned 'Rideout' Event

Kennerley said the motorcycle was estimated to be going 80 to 90 mph when it went through that line of warning flares and hit the rear truck in the caravan about 5:44 a.m.

READ MORE: Jefferson Award Winner Aims To Bridge Digital Divide Among Bay Area High School Students

In addition to the flares, Kennerley said, there were signs posted about the maintenance work under way, which he said was routine.

The motorcyclist was declared dead at the scene. His name was being withheld pending notification of his next of kin.

MORE NEWS: UPDATE: Suspect Arrested After 94-Year-Old Asian Woman Stabbed In San Francisco's Tenderloin Neighborhood

The cause remains under investigation.