Lewiston, ME – LEWISTON (AP) — Investigators say natural gas was the cause of Monday’s spectacular explosion in downtown Lewiston that injured five people and blew out windows along a stretch of Lisbon Street.

Fire Chief Michel Lajoie said the gas came from a Northern Utilities distribution pipe that ran in front of the Main Street building housing Lewiston Radiator Works. But it’s not clear how the gas got into the building and how it was ignited.

Investigators said cold weather may have been a factor because the gas ran through an older model of pipe that’s less flexible and does not hold up as well when the ground freezes and thaws.