Crews working on the overpass ran into hazardous materials that needed to be cleared before they could proceed.
They also found an AT&T fiber-optic line in the bridge that affected customers in the area. It was unclear how much longer the reopening would be delayed, but Caltrans said the closure could last until Saturday.
Caltrans officials say Wednesday's tanker fire did so much damage to the Paramount Blvd. overpass that they will have to demolish the east portion.
As of 3 p.m. Thursday, the closure on the westbound 60 was shortened. The westbound closure limit has been moved to Rosemead Boulevard from I-605. This allows motorists to continue their commutes further on westbound SR-60 to exit at Rosemead Boulevard. The freeway connector transition from northbound and southbound I-710 to eastbound SR-60 remains closed, according to Caltrans.
Caltrans expects to have the bridge completed Friday afternoon in order to reopen the freeway before rush hour.
The tanker burst into flames along the eastbound lanes at about noon Wednesday and burned right under the overpass for hours.
"You have extreme temperatures, you have the concrete actually popping and crumbling, kind of like popcorn in a way," said Caltrans spokesman Patrick Chandler.
Caltrans officials say the demolition and repair is similar to what was done on the 405 Freeway during "Carmageddon," but without all the time for planning. Crews are moving quickly.
"They've already put down sand and gravel on the eastbound side to catch any of the falling debris that they're going to knock down," Chandler said.
Two-hundred firefighters battled the flames that were fueled by the 8,800 gallons of gasoline on board the tanker Wednesday.
Crews worked through the night to clean up the mess. Workers removed what was left of the tanker, and hazardous-materials crews were able to contain the fuel that spilled onto the freeway.
The driver of the truck and his passenger were not injured. A firefighter battling the blaze fractured his leg.
The cause of the fire remains under investigation.
Commuters were urged to plan ahead before leaving their homes.
"Take the time to plan and look for alternate routes," California Highway Patrol Sgt. Denise Joslin said. "Print up those alternate routes. Have them with you when you get in the car so that you're not distracted by looking at your cellphone or your navigation device.
Residents with long commutes said they have to make adjustments.
"I normally get on [the 60 Freeway] on Paramount and now I have to get on about two onramps away, so it's definitely inconvenient," said Peter Apotaca, who has to commute to Marina del Rey.
Drivers can take surface streets such as Valley, Beverly, Olympic and Whittier boulevards or other main corridors such as the 10, 210 and 605 freeways.
For those who want to avoid sitting in bumper-to-bumper traffic, public transit may be the best bet. Metrolink offers three different lines to downtown L.A.
There's the San Bernardino Line, which includes a dozen stops between San Bernardino and Union Station, and the Riverside Line, which runs between downtown Riverside and downtown L.A.
There's also the 91 Line, which runs between downtown Riverside and Union Station.
All Metrolink tickets also give riders the ability to connect to buses and light rail service in the area.