NEW YORK (AP) — What appear to be human remains were found in a chimney at a New York City school on Tuesday, a few days into summer break, police said.

It’s unclear how long the remains had been there or how they got there. Police are investigating, and city medical examiners are to determine what caused the death.

Officers were summoned around 9 a.m. to the public elementary and middle school in Queens and were told of the find. Police and the city Department of Education said no students were there at the time — Friday was the last day of school, and the building is closed for construction this summer. City Buildings Department records show recent permits for wiring, hot water heating and other work.

The City Department of Education called the discovery “deeply upsetting and concerning” and referred questions about the probe to police.

A call to the school rang unanswered Tuesday.

The school, called P.S./I.S. 113 Anthony J. Pranzo, enrolls about 750 students in prekindergarten through eighth grade.