LOS ANGELES (CBSLA.com) — A school bus on its way to Mark Twain Middle School ended up on top of a parked car at the end of a chain-reaction crash in South Los Angeles Friday morning.

The crash happened at about 6:50 a.m. at 66th Street and Normandie. Police said the accident was caused by a car that blew a stop sign on 66th Street and out onto Normandie, forcing drivers in both directions to take evasive action.

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A southbound vehicle, a white SUV, served over the double-yellow line and into the northbound bus, causing it to swerve and smash into two parked, unoccupied cars. One of the cars was dragged about 50 feet, and the bus came to rest on top of another car.

The driver who ran the stop sign left the scene, police said.

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Seven children were aboard the bus at the time of the crash. Four students were hurt, but not seriously, while the bus driver was taken to a hospital for an unspecified medical problem, according to the Los Angeles Fire Department. The driver of the SUV that swerved into the bus was also taken to a hospital.