Update 3:42 p.m.
Caltrans says some lanes of the northbound 15 freeway are now expected to open at 6 p.m. in instead of 4 p.m.
Update 12:28 p.m. Some lanes to re-open Tuesday afternoon
Caltrans hopes to reopen some lanes of northbound 15 in the Cajon Pass this afternoon. The freeway has been shut down in Hesperia since yesterday when a bridge over the freeway caught fire. That bridge had been under construction and will have to be rebuilt.
Caltrans spokeswoman Terri Kasinga said that crews are trying to demolish a portion of the bridge on the northbound side and put up temporary railing.
"So with the K-rail - if they're protected from anything overhead and it's been removed it's looking pretty good for possibly getting one or two lanes open for four o'clock," Kasinga told KPCC.
Caltrans hopes to reopen southbound lanes sometime tomorrow.
"They’ll try to get some lanes open and then probably go back ... and do some pavement work," said Kasinga. "The lanes may be a little rough but they’ll get traffic onto those lanes as quickly as possible."
Kasinga said traffic through the area has improved a bit today and advises drivers to check Caltrans' twitter @CalTrans8 for updates.
-- KPCC's Rob Strauss and Ashley Bailey
Officials say northbound lanes of Interstate 15 in Hesperia could be reopened by the afternoon as crews try to extinguish a fire still burning at a bridge construction site.
Caltrans said early Tuesday that traffic on the northbound lanes of Southern California's main connector to Las Vegas could be flowing again in time for the evening commute. Southbound lanes are expected to reopen by Wednesday morning.
Commuters are urged to find alternate routes, including interstates 138 and 18. Interstate 15 was closed around 1:30 p.m. Monday because of falling debris.
San Bernardino County Fire Capt. Josh Wilkins says the blaze was started when a construction worker's blowtorch accidentally ignited the wooden supports of the Ranchero Road overpass bridge.
The fire burned all night, causing metal girders to sag into lanes below.