ROME — A blaze, possibly sparked by a gas canister explosion, destroyed part of an historic bridge spanning the Tiber River in Rome before firefighters extinguished the flames early Sunday.

Firefighters said the fire erupted before midnight Saturday near the Ostiense neighborhood and by 4 a.m. Sunday they had completed their work.

No one was injured in the fire that involved the Industry Bridge, but three nightclubs near the riverside neighborhood popular with young people were evacuated as a precaution, Italian state TV said.

The blaze appeared to have started in an area of shacks occupied by homeless people on the river banks near Industry Bridge before spreading to the span itself. State radio said authorities believe the fire might have been started by an explosion of a cooking gas canister by one of the homeless people.

A section of the bridge’s outer pedestrian walkway and stretch under the roadbed carrying utility lines broke off and fell into the Tiber. State radio noted that another fire several years ago had also involved the shacks.

Firefighters said in a tweet that the bridge is currently too dangerous to be used. They also banned any navigation under it until the span can be repaired.

Pope Pius IX attended the 1863 inauguration of the bridge, one of the last major construction works in Rome in the waning years of the papal state controlling the city, which would soon become the capital of unified Italy.

Dubbed by Romans the “Iron Bridge,” the span originally served as a railway bridge. Later it was outfitted to instead serve cars and foot traffic.

A plaque near one of the span’s ends pays tribute to 10 women who were executed on it in 1944 by German SS troops occupying Rome during the latter years of World War II. The women were punished for having occupied a bakery to feed their families in the city where war made food scarce.