Fifty vehicles piled up in a chain-reaction accident in dense fog Tuesday, scattering mangled cars along a 3-mile stretch of highway and injuring as many as a dozen people, the California Highway Patrol said.

The crash, reported just before 8:20 a.m., shut down part of the southbound lanes of Highway 99 south of Fresno.

Rescue crews had to cut three people out of a car that slammed into a tractor-trailer rig, CHP Officer Joseph Miller said. One woman was unconscious and pinned in her car for almost two hours while crews worked to pry her out.

"We had to systematically go through and remove the dashboard and cut the top off ... to safely get access to that patient," said Mike Bowman, a spokesman for the California Department of Forestry and Fire Protection.

"We had about 10- to 15-foot visibility so I know it was even thicker when this wreck transpired," Bowman said.

Matasha Bailey, who was commuting from Fresno to Tulare, jumped out of her car to avoid being hit after she heard cars crashing in the haze around her.

"It seemed liked metal crashing, crushing so I got out of my car and jumped the divider right here on the highway and just kind of waited on the other side of the freeway till I heard that it was clear," she told ABC-30. "It's amazing. I just feel like it's God's will because I should have been in this accident as well."

Tow trucks worked to remove big rigs covering the entire southbound portion of the freeway as crash victims gathered on the freeway shoulder near the wreckage.