MINNEAPOLIS (AP) — A preliminary report about an explosion at a Minneapolis school says a maintenance worker smelled natural gas and used a radio to tell others to evacuate just a minute before the blast.

The preliminary report into the Aug. 2 explosion at Minnehaha Academy was released Monday by the National Transportation Safety Board. Two people died when part of a building collapsed.

The NTSB says natural gas was released as workers were moving gas meters from the basement to outside the building. The NTSB has said that moving gas meters is a "hazardous operation."

Minnehaha Academy is a private Christian school serving students from pre-kindergarten to 12th grade. The blast affected the campus that houses the high school. Classes there will start two weeks late, on Sept. 5.

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