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UPPER DARBY, Pa. (CBS) — Upper Darby Police Superintendent Michael Chitwood rejects the claim of a school official that a student was stabbed with a pencil.

The Upper Darby School District superintendent Dan Nerelli tells parents in a letter that a 15-year-old freshman stabbed by another student with a pencil at the high school on Monday afternoon has been released from the hospital.

Chitwood said he rejects what Nerelli put out.

He said numerous interviews conducted with medics and the treating physician at Lankenau Hospital confirmed to his detectives the wounds were consistent with that of a knife.

Chitwood said the juvenile suspect, at first, claimed to detectives he had used a pencil and Chitwood said he’s willing to put his 54 years as a police officer on the line.

Police are investigating a stabbing at Upper Darby High School. (credit: CBS3)

The complete letter sent by Nerelli reads as the following:

“Yesterday, two freshman students engaged in an altercation in a stairwell just prior to dismissal. During the altercation, one student used a pencil to puncture the arm and back of the other student. The injured student was evaluated at the hospital and has since been released. He is expected to recover fully,” the superintendent said in a letter.

Superintendent Dan Nerelli, responding to a request for comment, said their statement was based on information they were provided.

The incident happened in a stairwell shortly before dismissal, police say.

A 14-year-old suspect in custody.

Police have not reported the motive behind the stabbing but they say they believe the two students knew each other.