WAHPETON (AP) - Authorities think a bird's nest in a chimney caused a Wednesday night fire that damaged the roof of a building on the North Dakota State College of Science campus in Wahpeton.

Schuett Hall, an auto-shop classroom building, was open for classes Thursday.

College spokeswoman Barbara Spaeth-Baum says a firefighter suffered a knee injury while cutting away a section of the roof to fight the fire. No students or staff members were injured.