LA JOLLA (CBS 8/CNS) - A box truck rear-ended a stalled sedan on Interstate 5 near La Jolla early Thursday, sending the car's driver to a hospital with life-threatening injuries.

The car was struck in the northbound lanes near Nobel Drive shortly before 1:30 a.m. The box truck pushed that vehicle down the freeway, trapping the female driver inside.

Then the driver was extricated from the wreckage and taken to Scripps Memorial Hospital La Jolla, according to the California Highway Patrol and the San Diego Fire-Rescue Department.

The box truck, carrying two tons worth of fish, overturned following the crash, but its driver apparently avoided serious injuries.

The crash left three northbound lanes blocked, authorities said. A SigAlert was in effect for more than three hours. All lanes of northbound I-5 have reopened.