A big rig veered off the northbound Interstate 5 on Friday and rolled down an embankment, seriously injuring the driver and sole occupant, California Highway Patrol officials said.

The truck was northbound north of Hasley Canyon Road around 3 p.m. when it swerved to the right for unknown reasons, said CHP Officer Eric Priessman. The big rig tumbled off the freeway and rolled over at least once, crashing through a chainlink fence, he said.

The driver had to be extracted by Los Angeles County firefighters and taken to the hospital, Priessman said.

His identity and condition were unknown, but he was still at the hospital Friday evening, the officer said.