MINNEAPOLIS (NBC) -- We now know the cause of a 2017 explosion that killed two people and badly damaged a high school in Minneapolis.
A report released Monday by the National Transportation Safety Board says the explosion and fire at the Minnehaha Academy was caused by human error.
According to the NTSB findings, workers for a natural gas supplier mistakenly thought a gas valve was turned off when they attempted to move gas meters.
Federal investigators concluded the blast happened because a pipe-fitting crew lacked proper training and wasn't fully authorized to move a gas meter.
The explosion killed two people, injured nine others and caused $30 million in damage at the private Christian school.
School was out for the summer, but some programs were in session.
About 42 staff members and students were evacuated from the school immediately before the explosion.