The crash occurred around 3:24 p.m. Tuesday. It was believed there were 36 people on board the bus when it overturned.
The CHP Gilroy office sent its multi-accident investigation team to the scene. Ambulances and helicopters were also sent.
The highway was shut down in both directions after the accident. The northbound lanes reopened hours later.
The bus is owned by Orion Pacific, out of Orange, California.
The Associated Press contributed to this report.
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