LEWISTON – Investigators waded through a ton of debris and a basement filled with dark water Tuesday as they sought the cause of an explosion that ripped through a Main Street business a day earlier.

Officials said the blast originated in the basement of the former Hotel Holly and natural gas may have been the culprit.

Investigators remained at the scene until nightfall Tuesday, trying to finish up their work before arctic temperatures moved into the area.

“We’re trying to eliminate all types of possible sources,” said Lewiston fire Chief Michael Lajoie. “The explosion was a large one. It displaced many things.”

By the end of the day, investigators said natural gas was a likely cause of the explosion, although they were not ready to make a final ruling.

Natural gas was once piped into the old hotel but the supply was capped off years ago, fire investigators said. A six-inch natural gas main runs under Main Street, not far from the scene of the Monday afternoon blast.

The explosion caused the former Hotel Holly to collapse and the building later burst into flames. Next door, Lewiston Radiator Works was battered and singed and two employees were forced to flee.

“They were lucky,” said State Fire Marshal’s Office investigator Dan Roy Jr. “The brunt of the blast went out through the old hotel.”

Richard Hollis, who owns Radiator Works, was inside the small, cinderblock building with another employee when the building next door blew up.

“They felt like a tornado him them,” Roy said.

Those two men suffered minor injuries. Three other people who were passing the building were injured when the concussion blew windows from their vehicles. Debris hurled from the explosion was found Tuesday 380 feet away from the scene of the blast.

Lajoie said crews had to plow through rubble and pump water from the basement of the old Hotel Holly in order to begin their investigation.

At the time of the explosion, the former Hotel Holly was used as a warehouse for Radiator Works, Lajoie said. In the wreckage, investigators found air conditioning equipment, radiators, empty gas tanks and tires.

Fire officials said the building was supplied with electricity and that a small office was housed in the rear. The building was heated by an oil furnace.

Officials from Northern Utilities were called in to examine the pipes that used to supply natural gas to the building.

Meanwhile, damage caused by the explosion was evident Tuesday. Windows along Main, Canal and Lisbon streets were either boarded up or replaced.

Roy said damage around the area reflected a “three-sided blast.” He explained that the wave from the initial explosion bounced off Bates Mill No. 5, then off the former Empire Theater building, before traveling down Lisbon and Canal streets.

Hollis and his employee were rattled but not seriously hurt because the blast exploded away from them, according to the inspector.

State and local fire investigators planned to return to the scene on Wednesday.

Police said no looting or other problems arose at the businesses with windows blown out from the blast. Extra officers were sent out onto the streets Monday night and others were working overtime on Tuesday.

Agents from the federal Bureau of Alcohol, Tobacco and Firearms, originally notified about the explosion, were not needed at the scene, police said.