A Southwest Mercer County Regional policeman spotted the fire at 1:16 a.m. and called 911, firefighters said.

The fire started in the back of the building at 208 Roemer Blvd., in an brick addition, firefighters said. Fire was shooting out windows by the time firefighters arrived.

Firefighters thought someone might have been in an upstairs apartment and called Sharon and Hermitage firefighters for assistance, but it was later determined no one was inside, firefighters said.

The cause of the fire is undetermined. A state police fire marshal has visited the site and Southwest police are investigating, firefighters said.

The fire damaged a porch on the rear of Roamer's Bar at 204 Roemer.

The building is insured.