MURRYSVILLE — Twenty students were injured, four seriously, in a multiple-stabbing incident this morning in Franklin Regional High School.

Westmoreland County public safety spokesman Dan Stevens said a suspect, also a student, is in custody and was being questioned by Murrysville police and Westmoreland County detectives.

Those seriously injured were flown to hospitals by medical helicopter. Some of the 20 injured students suffered stab wounds to the extremities, he said.

None of the injuries was life-threatening, he said.

The injured students’ ages range from 14 to 17.

Just before 7:15 a.m., a school resource officer asked for medical assistance at the school for a stabbing. The students were injured in several classrooms and in the hallways before the classes started, Stevens said.

Parents of the injured students were being contacted.