Traffic is bumper to bumper as people scrambled to find alternate routes on  Friday, March 31, 2017. Many commuters in some of Atlanta's densely populated northern suburbs will have to find alternate routes or ride public transit for the foreseeable future after a massive fire caused a bridge on Interstate 85 to collapse Thursday, completely shutting down the heavily traveled highway.  (AP Photo/Alex Sanz)
Traffic is bumper to bumper as people scrambled to find alternate routes on Friday, March 31, 2017. Many commuters in some of Atlanta's densely populated northern suburbs will have to find alternate routes or ride public transit for the foreseeable future after a massive fire caused a bridge on Interstate 85 to collapse Thursday, completely shutting down the heavily traveled highway. (AP Photo/Alex Sanz) Credit: Alex Sanz

Atlanta’s dreadful rush-hour traffic could be extra nasty for months to come after a raging fire underneath Interstate 85 collapsed an elevated portion of the highway and shut down the heavily traveled route through the heart of the city.

Traffic was bumper to bumper on nearby streets as drivers were forced to take a detour Friday, the morning after the blaze caused the concrete to crumble.

The collapse took place a few miles north of downtown, and the effects could fall most heavily on commuters from Atlanta’s densely populated northern suburbs. They will have to find other routes to work or ride mass transit.

Connie Bailey-Blake, of Dacula, 37 miles northeast of Atlanta, waited for a MARTA commuter train to reach her job downtown. She typically drives, often by way of the interstate.

“I’m supposed to be at work at 9 a.m. and it’s 9:15 a.m.,” Bailey-Blake said. “The first few days are going to be difficult. This will be my new life.”

Amelia Ford picked a new route to work by car and said it took her 45 minutes to travel 3 miles from her Atlanta home to the nearest open on-ramp to the interstate.

Georgia Transportation Commissioner Russell McMurry said 350 feet of highway will need to be replaced in both directions on I-85, which carries about 400,000 cars a day through the city and is one of the South’s most important north-south routes.

He said repairs will take months but declined to be more specific.

The collapse effectively “puts a cork in the bottle,” Georgia State Patrol Commissioner Mark McDonough said.

The fire broke out Thursday afternoon in an area used to store state-owned construction materials and equipment, sending flames and smoke high into the air. Fire authorities said they had not determined how the blaze started.