Law enforcement officials could not immediately identify the cause of the explosion, but said an odor of natural gas was apparent, the New York Times reported.
Rockland County fire and emergency services coordinator Gordon Wren said a fire alarm was pulled in the building around 9:45 and an officer from the South Nyack Police Department said a loud noise could be heard around the same time.
Several people were trapped in the rubble, and one woman was blown out a second-floor window and suffered back and neck injuries, Wren said.
The site of the explosion was the school's Sky Island Lodge, a two-story building purchased by the school in 1998, which housed classrooms and a computer lab.
2014: The Year in Music [PHOTOS]