An explosion at a Minneapolis school has left at least five people injured and two others unaccounted for. The blast is believed to have been caused by a gas leak, according to Minneapolis police. Police said five people were taken to a local hospital for treatment while one person was treated at the scene.

Three people are thought to have been on the roof of Minnehaha Academy near the center of the city at the time of the incident, police told a press briefing. It is not clear whether the two remaining missing people are under the rubble. There was also no indication from authorities if the missing were staff or students.

They also reported that part of the partially-collapsed building was on fire when they arrived at the scene. Emergency crews are working on extinguishing the blaze.