Firefighters remain at the scene after putting out a fire at the Fireside Inn and Suites on Riverside Street on Wednesday night. Brianna Soukup/Staff Photographer

Firefighters are investigating the cause of a fire that damaged a room at Fireside Inn & Suites in Portland on Wednesday evening and caused one guest to be treated for smoke inhalation.

The fire started around 6:30 p.m. in an unoccupied guest room on the second floor of the motel at 81 Riverside St., off outer Brighton Avenue, Deputy Fire Chief Mike Nixon said.

A guest in an adjacent room was overcome by smoke, assisted from the motel by firefighters and given medical attention by paramedics on the scene, Nixon said. The guest recovered and declined transportation to a hospital, he said.

Other guests evacuated from that part of the motel were moved to other rooms. Firefighters left the motel around 9 p.m.

The fire didn’t appear to be suspicious but remained under investigation Wednesday night, Nixon said.