PARIS — Fire engulfed the town hall of Paris’ 12th district early Monday, causing no casualties but severely damaging the bell tower of the 19th century building.

Paris police prefect Laurent Nunez said the fire broke at 3:20 a.m. in the roof of the building. About 150 firefighters battled the flames and the fire was extinguished in the morning, Nunez said.

He warned there was a “risk of collapse” of the upper part of the bell tower. A security area has been set up around the building.

An investigation will seek to determine the causes of the fire, Nunez said.

Paris mayor Anne Hidalgo praised in a statement the “exceptional intervention” of the Paris fire department and said “all public services for residents have been maintained and will be provided in the 11th district town hall.”

The 12th district town hall was built in 1876 with a 36-meter (118-foot) high bell tower on top of its main entrance.