LOS ANGELES (Reuters) - At least five people died when the charter bus they were on crashed into a pole by a highway in Northern California early on Tuesday, officials said.

Images from Sacramento television station KCRA showed the pole for an exit sign sliced lengthwise through the bus, from its front to its middle.

The bus was en route to Sacramento from Southern California at about 3:30 a.m. PDT (1030 GMT) on State Route 99 when it crashed, California Highway Patrol spokesman Moises Onsurez said by phone.

Highway Patrol officials said the cause of the crash near the town of Livingston was under investigation.

At least five people on the bus were killed, Onsurez said.

Several passengers were airlifted to local hospitals, Onsurez said, but he could not immediately say how many were injured.

Six people with major injuries were airlifted to hospitals in the region and 15 others were taken by ambulance to various hospitals, according to Sacramento-based television station KCRA.

"The bus split open and that's how I got out," Jennifer Rivera, a child who survived the crash, told KCRA. "My arm was scratched and it hurt a lot."

The bus driver suffered major injuries, according to the San Francisco Chronicle.

Local media reported the bus suddenly veered off course. Roughly 30 people were on board at the time, television station CBS Sacramento reported.

The National Transportation Safety Board has sent a team to investigate the crash, Eric Weiss, a spokesman for the federal agency, said in an email.

(Reporting by Alex Dobuzinskis in Los Angeles and Laila Kearney in New York; editing by James Dalgleish and Andrew Hay)