SAN ANTONIO — A school bus struck another bus on Monday, killing one of the drivers, officials said.

Steve Linscomb, a spokesman for the Judson Independent School District, said the collision happened outside a high school. He said about 80 students were on both buses and that none of them were believed to have been seriously hurt.

Linscomb said the crash killed a woman in her 60s who was driving a bus from the San Antonio Independent School District.

He said it was not immediately clear if she died in the crash or had a medical emergency before the accident.

The bus jumped a median before hitting the second bus head on and striking a fence. The woman was pronounced dead after being thrown from the bus upon impact.

Police said three students were taken to the hospital for treatment of minor injuries.

Investigators said the woman, who had been working for the school district since 1999, had passed a mandatory physical examination in August.

The crash occurred outside Wagner High School. Classes were held as scheduled at the school, but part of the roadway where the accident occurred was blocked to traffic.