Saco, ME- WMTW-TV – A propane leak in a vacant second-floor apartment. That, according to investigators, was the likely cause of Tuesday night’s explosion in Saco that reduced a four-unit apartment building to rubble.

Investigators from the Maine Fire Marshal’s office made the determination following a visit to the blast scene on Elm Street.

Three people were taken to a Biddeford hospital, but officials say their injuries were not life-threatening.

Firefighters rescued a woman who was trapped in what was left of the building’s second floor. Another occupant made it out on his own, and a third was outside at the time of the explosion