Electrical wires sparked the Pratt Institute fire that burned dozens of students’ art projects last week, officials said.

The FDNY revealed today that the raging four-alarm inferno was accidental. It ignited on the sixth floor of the historic building on Willoughby Avenue around 2:15 a.m., Friday and injured three people.

Three firefighters were treated for minor injuries at Brooklyn Hospital and one civilian refused medical attention, officials said.

The structure, know as the Main Building, was built in 1887 and is on the National Register of Historic Places.

kconley@nypost.com