HESPERIA (CBS/AP) — All lanes of Interstate 15 in Hesperia remained shut down Monday night as crews battled a bridge fire ignited by a welder’s torch.

The fire was reported around 1:30 p.m. at the Ranchero Road overpass construction site, according to the San Bernardino County Fire Department.

LISTEN LIVE TO KNX 1070 FOR LIVE TRAFFIC UPDATES

The cause of the fire was determined to be from a rebar cutting operation in which blowtorches carried fire into the falsework of the bridge. Workers reported initial extinguishment efforts were unsuccessful due to high winds.

A civilian was treated for smoke inhalation. No further injuries had been reported at press time.

Firefighters were meanwhile expected to remain on the scene throughout the night, Caltrans spokeswoman Terri Kasinga said.

Officials said falling debris and damage to the structure could result in the closure of the 15 freeway for up to 48 hours.

“Thirty-six to 48 hours is the very earliest that it could possibly happen,” Caltrans spokesperson Michelle Profant told KCAL9’s Crystal Cruz.

Traffic remained backed up for miles on Monday night, with major delays through the Cajon Pass.

Motorists in both directions were being taken off at the Ranchero exits, which were temporarily opened to re-route traffic.

Some drivers were held up in traffic for as long as four hours, with vehicles backed up for 15 to 20 miles.

“I’ve never seen in my life such a mess. Everyone was driving on the shoulder, and then merging. And then people were driving recklessly. It was terrible,” one driver said.

Dozens of firefighters continued to battle the blaze in windy conditions, with limited access to water, and high danger that the wooden skeleton of the football-field-sized bridge would collapse. San Bernardino County Fire Department reported gusts surging up to 35 mph.

Caltrans crews worked into the evening demolishing remnants of the structure, which was scheduled to open in the summer of 2015.

Its contractors were still working on top of the bridge when the fire erupted, and were unaware of the blaze until being evacuated by firefighters because the flames were being pushed away by the wind.

Construction on the $59 million project began more than a year ago, according to Caltrans.

Structural engineers are expected to examine the overpass in its entirety to determine how much damage has been done and how much can be saved.

Insurance adjusters were also on the scene.

It remains unclear who will pay for the demolition.

(TM and © Copyright 2014 CBS Local Media, a division of CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2013 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)