An unidentified man was struck by a truck and killed Thursday night as he bicycled along Highway 20 on the east side of Clear Lake, the CHP reported.

The man's name and age hadn't been determined. He was not wearing a helmet, the CHP said.

Officers said the man was riding a black 10-speed bike on Highway 20 eastbound east of Keys Boulevard around 9:30 p.m.

A 2003 GMC Sonoma driven by William Hartman, 68, of Yuba City was headed in the same direction when he struck the bicyclist from behind, the CHP said. Hartman told officers he didn't see the bicyclist, who was wearing dark clothes.

The bicyclist died at the scene. Alcohol doesn't appear to have been a factor in the collision, the CHP said.