WELLS — The fire that destroyed an apartment building and displaced more than a dozen families in Wells on Monday night was started by the “careless disposal of smoking materials,” the Office of State Fire Marshal said.

Investigators determined that the fire started near a wooden porch along the outside of Pine Tree Commons, Department of Public Safety spokesperson Shannon Moss said in a statement Tuesday afternoon. The fire marshal’s office was called to the apartment building at 2124 Sanford Road at about 7:40 p.m. Monday.

All the building’s residents escaped the blaze safely, though one firefighter sustained minor injuries, the Wells Fire Department said in a statement early Tuesday.

The fire hit four-alarm status, burning approximately half of the complex’s roughly 20 units. The building is a complete loss, the department said.

Wells Fire Chief Mark Dupuis said the fire began in a bucket full of ash and cigarette butts, which sat a few feet from the building’s three-story wooden deck.

“The fire actually caught the structure – caught the railings on fire – and just moved dramatically fast through the setup,” Dupuis said on a Monday evening phone call.

By the time crews arrived, the flames had engulfed the entire deck structure and breached the main building’s walls, he said.

Roughly 20 crews from surrounding communities, including from as far as New Hampshire, helped combat the blaze, the department said. Dupuis estimated that between 80 and 100 firefighters responded, though others responding Monday night said it could have been more.

Initial crews arrived with one tanker truck of water and two engines, but they quickly exhausted the thousands of gallons it held, Dupuis said Monday night. The property does not have a pressurized fire hydrant, nor did it have a sprinkler system, he said.

To ensure a steady flow, crews then set up a pool of water on Sanford Road, which was constantly refilled by a stream of tanker trucks from Kennebunkport, Eliot and beyond. That water traveled more than 100 feet down snaking fire hoses before reaching the flames.

Though part of the building avoided direct fire damage, the entire building is uninhabitable, leaving 16 families displaced, Dupuis said, adding that he was not sure how many individuals were affected. Two households are staying with relatives nearby, while the other 14 are in a local hotel, he said.

One firefighter was injured when a piece of debris fell onto his shoulder, Dupuis said. Firefighters used a chainsaw to cut into the building’s walls to reach deep flames.

Property owner Marty Devlin blocked non-resident cars from entering the parking lot around 5 p.m. Tuesday evening.

Devlin said he was “getting things buttoned up” at the property and that several people had stopped by to look at the damage. He adjusted a line of yellow tape that ran between two “NO TRESPASSING” signs and covered the driveway.