A man who crashed into the Nicasio Reservoir and died was identified Tuesday as Richard Louis Giacomini, 71, of Point Reyes, Marin County sheriff-coroner's officials said.

Giacomini was heading west on Point Reyes-Petaluma Road when his truck drifted off the road at 5:49 p.m. Monday and hit a guardrail, Lt. Keith Boyd said.

The 2007 Chevrolet Silverado pickup overturned, plunged into the reservoir and was submerged when emergency crews arrived.

The Marin County Sheriff's Office dive team retrieved the driver and searched for possible passengers. But the driver appeared to be alone and was pronounced dead at 6:42 p.m.

Coroner's staff completed a forensic examination Tuesday, but Boyd said the cause of death was still under investigation.