SAN DIEGO -- A stubborn blaze that erupted early Thursday morning within the support structure of the historic Cabrillo Bridge closed the 125-foot-tall Balboa Park landmark, along with the freeway that runs underneath it.

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SR 163 Closed After Bridge Catches Fire

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Smoke began pouring out of manholes and joints on the 90-year-old landmark span over state Route 163 at Laurel Street about 4:30 a.m., according to the San Diego Fire Department.

Engine crews found flames spreading over wooden scaffolding that was being used to retrofit the western side of the bridge, SDPD public information officer Maurice Luque said.

Electrical equipment may have sparked the non-injury blaze, according to investigators, who also were looking into the possibility of arson.

Firefighters drilled holes in the bridge to pour water and foam on hot spots that flared and smoldered into the afternoon, Luque said.

"We've had to take a real creative approach to this fire because it's been difficult to access. We're using Urban Search and Rescue equipment as well as Hazmat monitoring equipment to determine where the hot spots are and what the condition is inside the bridge," Luque said.

Heat from the fire may have damaged the structure's steel supports, Luque said, adding that wooden supports that helped frame the bridge were charred.

At about 5 a.m., the California Highway Patrol closed both sides of SR-163 between Interstate 5, just north of downtown San Diego, and I-8 in Mission Valley, CHP Officer Alicia Contreras said.

The northbound lanes were re-opened around 4 p.m., and the southbound lanes of the highway re-opened around 7:30 p.m.

San Diego Padres officials advised baseball fans planning to attend the team's game against the Tampa Bay Devil Rays Thursday night to avoid the SR-163 corridor entirely and use I-5, SR-94 or public transit instead.

The 405-foot Cabrillo Bridge was built between 1912 and 1914 as part of the Panama-California Exposition of 1915-16 at Balboa Park.

On April 12, 1914, future President Franklin Roosevelt drove the first automobile across the towering span while serving as secretary of the Navy.