A fire inside one of the towering pylons of the Cabrillo Bridge prompted a unique firefight Friday morning, which halted traffic on the highway underneath.

San Diego Fire-Rescue firefighters were called around 5:30 a.m. to a report that smoke was rising from under the historic bridge. When crews arrived, they determined smoke was actually coming from inside one of the pylons, and a confined space response would be necessary, SDFD spokesperson Jason Shanley said.

“Crews are going to go from the bottom and work their way up inside the pylon to try to determine what is actually on fire. Right now, it appears to be just rubbish at several levels inside the pylon,” Shanley said.

While the cause of the fire has yet to be determined, including whether it was set by someone gaining access to the area, Shanley said it appeared rubbish was on fire and that it is a type of call they have responded to previously.

“This has happened before. So this is a fire we’re used to,” Shanley said.

Once crews get inside, they’ll determine if there’s a need for an investigation.

SR-163 was shut down for the initial response and by noon, at least one lane still remained closed as city crews worked to weld the bridge, according to California Highway Patrol communication.

The Cabrillo Bridge was built for the Panama – California Exposition of 1915 and was dedicated on April 12, 1914, by then-Assistant Secretary of the Navy Franklin D. Roosevelt, according to the city of San Diego.