A massive fireball collapsed a portion of Interstate 85 in Atlanta, sending motorists driving through billowing black smoke before the city shut down that section of the highway indefinitely.
The fire started underneath part of the highway on Thursday evening. At about 7 p.m., an elevated section of the northbound interstate collapsed, forcing frantic motorists to seek alternative routes.
An estimated 250,000 cars per day drive through that stretch of the interstate -- a major thoroughfare for traffic heading north and south through Atlanta.
While the highway is normally jammed with cars around that time, there were no fatalities, Mayor Kasim Reed said.
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Social media users posted surreal images showing drivers vanishing into the black smoke on the highway as the fire burned beneath them.
CNN's Eliott C. McLaughlin was driving north on I-85 during evening rush hour when he saw smoke rising from underneath the elevated highway.
Many cars on the left side of the five-lane section barreled through the thick black smoke. They disappeared into the darkness as they drove, he said.
McLaughlin slowly followed the taillights of an SUV through the smoke.
Cortez Stafford, a spokesman with the Atlanta Fire Department, said the blaze was massive.
"There was a 40-feet or higher wall of fire. Power lines were falling and arcing heavily and falling in the streets," Stafford told CNN.
As concrete began falling from under the bridge, firefighters were asked to step back, Stafford said. "Not even two minutes later, the highway fell with a big 'kaboom.' (It) knocked our guys back."
Interstate traffic was stopped and turned around, creating jams that extended 5 miles or more. While that's not long by Atlanta standards, many drivers were stuck in the area for hours.
What caused the collapse?
As word of the incident spread, so did the speculation.
Atlanta Mayor Kasim Reed did not provide details on what caused the collapse, but said it is not linked to terrorism and an investigation is underway.
"We've spoken to the special agent in charge of FBI, there is no evidence this is related to terrorism," he said Thursday night.
Gov. Nathan Deal said he heard speculation it was caused by some "PVC products that caught fire."
In an unusual move, two fire trucks from Hartsfield-Jackson Atlanta International Airport in south Atlanta rushed to the scene and sprayed foam on the fallen section and flames.
'It's going to take some time'
Authorities worked through the night to access the bridge and ensure the risks from the collapse are contained.
"There is a possibility you could have a further collapse," Reed said. "We still have personnel at the sight making sure there is no hotspots. We won't know the area of vulnerability for the bridge until tomorrow."
All five lanes of the highway in each direction will be closed for the foreseeable future, officials said.
That prospect sent shudders through metro Atlanta commuters, who already contend with heavy traffic.
Officials scrambled to come up with alternate routes and encouraged commuters to use public transit.
Transportation authorities are trying to put together a traffic and detour plan for drivers.
Deal told reporters the company that originally built the elevated highway would assess the damage.
"It's going to take some time to get it repaired and to get it back in service," he said, without offering a time frame for reopening.
Not business as usual
MARTA, Atlanta's rail and bus system, will offer extended service through the weekend.
One school district, in nearby DeKalb County, canceled classes for Friday. Schools in Atlanta will be open, Reed said, and city and state offices won't open until 10 a.m.
The collapse happened at a crucial time. The Atlanta Braves will play the Yankees at a 7:35 p.m. home game, and next week is spring break for many schools in the Atlanta metropolitan area.
Weeks of repair ahead
Reginald DesRoches, a professor at Georgia Tech, said most structural materials lose strength when subjected to high temperature, meaning the concrete could have been compromised by the heat.
He said it is too early to say how long it will take to repair the highway.
"It certainly can take anywhere from several weeks to several months," he said. "The surrounding sections of the highway will be evaluated to determine if any damage was sustained from the heat. It is probably prudent to check both sides of the adjacent sections (northbound and south bound)."