Investigators say a gas worker looking for the source of a leak accidentally triggered the massive explosion in downtown Springfield, Massachusetts Friday night.
"We have determined that human error, not a fault in the gas infrastructure, is the cause of what the explosion was," said Massachusetts State Fire Marshall Stephen Coan.
The blast injured 18 people and destroyed several downtown businesses.
Still, the error was not the worker's.
It was in the markings on the ground incorrectly showing the location of the high-pressured gas line.