This reminds me of the school explosion in New London Texas in 1937,
A woman is dead, a man is missing and seven are in the hospital after an explosion caused a school building to collapse in Minneapolis today, the Minneapolis Police Department said.
The explosion set the building at Minnehaha Academy on fire and the flames were further fed by a ruptured gas line, according to police. The fire has since been put out, police said.
The Minneapolis Fire Department confirmed the explosion was caused by a gas leak and said contractors were doing construction on the gas lines at the time of the explosion.
https://www.yahoo.com/gma/minneapoli...opstories.html
In the case of the 1937 explosion, it was a build up of gas in the basement of the school, and someone flipped on a power saw, causing a spark due to that explosion that is why we have that rotten egg smell in gas. I bet there will be a law suit, against the construction company.