School administrators in New Rochelle say Isaac E. Young Middle School was broken into before school Tuesday.
Administrators told News 12 the break-in happened between 5:30 and 6 a.m. No students or staff members were in the building at the time.
The intruder came in through a window, which triggered the school's alarm system.
Police searched the campus when they arrived but couldn't find anyone. They're still not sure if anything was taken.
The start of the school day was delayed two hours due to the investigation, but dismissal took place at a normal time.