Hartford, CT- Investigators seeking the cause of Tuesday morning’s violent natural gas explosion on Willard Street say the apartment building’s 3-year-old furnace apparently allowed gas to leak for several hours prior to the blast.

The 6 a.m. explosion, at 50 Willard St., displaced 150 tenants but resulted in no injuries.

Hartford Fire Marshal Edward Casares said the explosion could have been prevented if tenants who reported smelling gas the night before had called the fire department.

Tenants told investigators they first smelled gas about 9 p.m. Monday, Casares said.

The gas apparently built up in the boiler room for hours, touching off an initial explosion about 3 a.m. Tuesday. “No one called the fire department. It shook the building. They looked out of the window and didn’t see anything and didn’t report it,” Casares said.

Three hours later, about 6 a.m. Tuesday, a series of explosions started in the boiler room, then moved to the upper floors as the gas escaped. “Right now, we are trying to investigate how [the natural gas] escaped,” Casares said.

The building’s owner, Hartford Estates, has been working with representatives of the Charter Oak Chapter of the American Red Cross to find housing for the tenants, said Paul Shipman, a spokesman for the Red Cross.

About 70 families were displaced, Shipman said. Two of those families were relocated to local motels, and the remaining families are staying with family and friends.

“Everyone who has applied has received help,” including food, bedding and prescription drugs, Shipman said. He said the Red Cross is working with 57 families who have requested aid.

The temporary shelter at the Pope Park Community Center was closed Tuesday night.

The apartment building sustained significant damage and remains closed to all tenants, and the utilities have not been turned back on.