Several people were stabbed at Franklin High School in Murrysville, Pa. on Wednesday, and a suspect was taken into custody, an emergency official said. Photo: AP.

Nearly two dozen students were injured at a western Pennsylvania high school Wednesday morning in an apparent stabbing spree.

The incident occurred at Franklin Regional High School in Murrysville, Pa., about 20 miles east of Pittsburgh. Dan Stevens, a spokesman for the Westmoreland County Public Safety Department, told CNN that 20 students were injured, four seriously, in the attack. The four were taken by helicopter to area hospitals, he said.

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Students leave campus after stabbings at Franklin Regional High School in Murrysville, Pa., on Wednesday. AP

A male student was in custody, he said, and there were no other suspects in the incident, Mr. Stevens said.

The attack occurred in a classroom and hallway at the high school before classes began for the day, according to Mr. Stevens. A 911 call was received at 7:13 a.m., he said.

The high school posted a notice on its website saying that the campus was locked down after “a critical incident” and said law enforcement was working with the school to manage the situation. The school advised parents to pick up students at a nearby elementary school.