WESTBROOK — A faulty light fixture has been determined to be the cause of a fire at Nano Dentistry at 13 Pleasant St.

The fire, which has been ruled accidental, likely started in a ceiling light  in the dentist’s office, said Westbrook Fire Chief Andrew Turcotte.

The two-alarm fire broke out close to 8 p.m. on Sunday, Dec. 30, just before residents across downtown Westbrook reported hearing a loud boom.

The Fire Department reported that when the first firefighters got inside the building, an oxygen tank at the dental office exploded.

“The percussion knocked two firefighters back into the hallway and to the ground, briefly disorienting all three members on the attack,” the department wrote on its Facebook page. “The percussion was heard by neighbors more than a half-mile from the incident and created significant structural damage to the rear of the commercial occupancy.

Residents of the two second-floor apartments had evacuated the building just before the explosion.

No occupants were injured nor were any firefighters, who got the fire under control by 11 p.m. Some firefighters stayed on site to make sure no further explosions occurred. Westbrook was aided in the response by firefighters from Falmouth, Gorham, Scarborough, Portland, South Portland and Windham.

The fire is being investigated by the State Fire Marshal’s Office.

Dr. Safwan Nano has operated his dental practice at 13 Pleasant St. since 2004, when he purchased the building, which dates back to 1890.

The American Red Cross is working with the six individuals displaced from their second-floor apartments to make sure they have food, a place to stay and other essentials.

The dentist office reported “we we were able to successfully access our hard drives and backup so we could continue to provide care as soon as we find a temporary location.”

Michael Kelley can be reached at 780-9106 or mkelley@keepmecurrent.com or on Twitter @mkelleynews.

The American Red Cross is working with residents and occupants of 13 Pleasant St. in the aftermath of a Dec. 30 fire that destroyed a dental office and two apartments   in the building.

The fire at 13 Pleasant St. in Westbrook was caused by a faulty overhead ceiling light that ignited an oxygen tank at Nano Dentistry Sunday, Dec. 30. No one was hurt in the fire, but the blast knocked down several firefighters and could be felt throughout much of downtown.