Firefighters quickly put out a fire at 10 Nassau Street in Princeton on Thursday morning.

The second floor of 6-10 Nassau Street in downtown Princeton caught on fire on Thursday morning. Firefighters were able to put the fire out in about 20 minutes but spent longer using thermal cameras to examine the building and make sure the fire didn’t spread. There were no injuries, officials said.

A manager a Coldwell Banker Real Estate entered the building Thursday morning, smelled smoke, and called 9-1-1. Firefighters had to open the walls and floors on the second floor of the building to make sure the fire was contained. Some beams in the building were burnt from the fire.

Bob Gregory, head of emergency services for the town, said the second floor where the fire started is vacant. The first floor suffered some water damage and smoke damage, he said. The cause of the fire has not been determined yet. The power had to be shut off for the building. The nail salon in the building is temporarily closed even though that part of the building did not suffer any damage. Workers are trying to see if power can be restored to just that portion of the building.

Nassau Street was closed at Bank Street for about an hour Thursday morning as firefighters worked at the scene.