Four people were flown to hospitals by helicopter, he said.
Dr. Chris Kaufmann at Forbes Regional Hospital in Monroeville, Pennsylvania, spoke to CNN on air. He said the facility is treating seven teens with stab wounds to their torso, abdomen, chest and back areas. He said that the injuries were "quite serious" and that "some are clearly life-threatening." An adult is also being treated there, he said.
The stabbings happened in classrooms and a hallway, Stevens said, adding that a suspect -- a male student -- was in custody.
A message on the Franklin Regional School District's website said all of its elementary schools were closed after the incident, and "the middle school and high school students are secure."
Information on what led to the stabbings and the conditions of the injured were not immediately released. The students range in age from 14 to 17, Stevens said.
The school is in Murrysville, about 15 miles east of downtown Pittsburgh.
Students were being released to their parents, Stevens said. Shortly before 10 a.m. ET, CNN affiliate KDKA reported that some parents were beginning to be reunited with their children.
(video courtesy: KDKA and WPXI for CNN Newsource)
(Allie Malloy and Ashley Fantz, CNN)
Copyright 2015 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.