LOS ALTOS HILLS — A tractor-trailer overturned on the southbound 280 freeway about a quarter-mile south of Magdalena Avenue on Monday afternoon, California Highway Patrol Officer Art Montiel said.

The truck loaded with rocks was blocking three lanes with traffic getting by in the fourth lane and on the shoulder, said Montiel. The accident, which was reported to the CHP at 1:55 p.m., led to traffic backups that lasted through the evening commute.

The call to the CHP came in at 1:55 p.m., and at 2:45 p.m. Montiel said it would be another two to three hours before the truck would be cleared.

Montiel said no other vehicles were involved.

The cause of the accident has not yet been determined, Montiel said.

The truck driver received minor injuries and was transported to Stanford Medical Center, Montiel said.

The driver’s name has not been released.