Caroline Hansen, a Saint Francis High School senior, considered one of the area’s best water polo players, was seriously injured in a multiple-car crash Saturday, according to a source close to the girl’s family.

Hansen was driving southbound on Interstate 280 near El Monte Avenue when she was broadsided on the passenger side by another car, said Curtis Glace, a spokesman for the California Highway Patrol. Hansen was on her way to the Lancers’ 7 p.m. Saturday home NorCal girls volleyball semifinal match against Rocklin when the accident occurred.

“It was a five- or six-car pileup,” Glace said. “We are not sure about the sequence of the vehicles, how they hit. We believe Caroline (Hansen) was hit at least twice, and that she was driving a sedan. There is a possibility that she took off her seat belt after she was initially hit, then was hit again.”

Hansen was taken to Stanford Hospital where she underwent surgery to relieve pressure around the brain, a source close to the family said, adding that she remained in a coma at the hospital’s intensive care unit after undergoing an MRI on Monday.

Hansen scored a goal in the Lancers’ 6-5 loss to Menlo-Atherton in the CCS Division I championship game on Nov. 20. The first team all-West Catholic Athletic League player scored three goals in the Lancers’ 4-3 CCS semifinal victory over Leland-San Jose.

The CHP, meanwhile, is continuing to investigate the accident.

“We are reviewing the 911 tapes,” Glace said. “There are people who called 911 whom we would like to talk to.”

The CHP is asking anyone who witnessed the accident to call 650-369-6261.