The Westbrook Fire Department responded Sunday night to a fire inside a building with a dentist’s office and residence in downtown Westbrook.

Dispatcher William Nelson said units were working to put out the fire at Nano Dentistry, 13 Pleasant St., between Main Street and William Clarke Drive. The fire was first reported between 8 and 8:30 p.m.

Nelson said there is at least one residential unit in the building, and that at least three residents had been displaced by the fire.

“They’re being assisted by the Red Cross,” he said about the displaced residents, whose names were not available.

The fire prompted temporary street closures in the immediate area so crews could connect fire hoses to hydrants across the street, Nelson said.

Nelson said the cause of the fire was unknown as of about 9:30 p.m., and that he expected firefighters to be at the scene until well into the early morning hours on Monday.