A colossal fire caused the collapse of I-85 in Buckhead at the height of rush hour Thursday evening, stranding thousands of motorists for hours and shuttering a main gateway to the heart of Atlanta indefinitely.

The bridge of northbound I-85 near Piedmont Road failed, just south of Ga. 400, about 7 p.m. as firefighters battled an intense blaze beneath the interstate. No injuries were reported. Authorities said they did not know what caused the fire, but the Georgia State Patrol said there was no evidence of a terrorist attack.

Carmen Dixon, 21 of Riverdale, said she was heading home from work in North Druid Hills. She said she could feel the heat as she passed the flames, which you hear her scream about at the end of the footage.

What authorities do know is no one will be traveling the busy stretch of interstate through the Capitol of the South any time soon. On Thursday night, the Georgia Department of Transportation declined to put a timetable on repair of the highway.

“Our primary concern right now is helping people reach their destinations tonight and tomorrow and in the future,” GDOT Commissioner Russell McMurry said late Thursday night.

He urged metro Atlanta residents to adjust their plans. “Consolidate trips. Don’t leave your home or business unless you absolutely have to to come to this part of the area,” McMurry said.

“The entire bridge has been compromised,” Atlanta Fire Department spokesman Cortez Stafford said late Thursday night. “Right now, it’s still dangerous to go under there.”

Even the parts that haven’t fallen down aren’t safe, Stafford said. The first firetruck on the scene just happened to be driving by, he said, adding that it took about 20 to 30 minutes for the bridge to collapse after firefighters arrived. The firefighters quickly determined the bridge wasn’t safe for anyone, Stafford said.

“We know from experience when you have a lot of heat on concrete it starts to crack and break. We saw it as a risk,” he said. “As they were fighting the fire, the concrete started to crumble. It was a close call.”

It is still too soon to determine the cause of the collapse since it’s still not safe to go underneath the bridge, he said.

Atlanta police on the scene said it could be hours or days before that stretch of Piedmont Road is open again to traffic, because authorities are concerned with potential structural damage that may have been done to sections of the freeway that stretch across Piedmont and that were adjacent to the fire.

» MORE: Photo gallery of past metro ATL traffic disasters

The bridge collapse sent governments and businesses scrambling to make plans for Friday. State and Fulton County government offices won’t open until 10 a.m. Meanwhile, DeKalb County told non-essential government employees to stay home, and that county’s schools will be closed.

Gov. Nathan Deal declared a state of emergency, saying the state is “mobilizing all available resources to ensure public safety and minimize disruption of traffic as we continue emergency response efforts.

“The Georgia Department of Transportation is coordinating response efforts with the Georgia Department of Public Safety (DPS), the Georgia Emergency Management and Homeland Security Agency, and other state and local officials,” Deal said.

This is the fire that began the blaze which brought down a bridge on I-85.

Credit: WSB viewer

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Credit: WSB viewer

“As this safety investigation and bridge assessment continues, we encourage the public to avoid the affected area, remain patient and allow first responders to perform their jobs,” the governor said. “We will continue updating the public on alternative traffic routes and other information as it becomes available.”

“This is as serious a transportation crisis as we could have,” said Atlanta Mayor Kasim Reed. “The governor has been leading and we have been acting on it. Our primary concern, first and most important, is that no one has lost their life. And as we stand here right now, we think that’s the situation.”

“It’s going to take some time to do a thorough assessment to determine what damage has been done to that section” of the bridge, Reed said. He said the city is working with the state to secure the area, but is wary of moving too quickly “because there is a possibility you could have a further collapse.”

MARTA spokesman Eric Burton said the agency plans to increase the frequency of trains on Friday and beyond to accommodate more passengers. He said extra employees would be on hand to assist passengers.

“MARTA seems like your best bet to get out of the city,” Burton said.

Capt. Mark Perry of the Georgia State Patrol said terrorism is not suspected in the fire.

Channel 2's Jason Durden uses new technology to pinpoint where the bridge collapse happened.

A bridge collapse of this type would be impacted by a combination of the fire temperature and duration of the fire, said Kim Kurtis, a professor in Georgia Tech’s school of civil and environmental engineering.

Kurtis is not familiar with the construction of this particular bridge, but generally speaking, “if this were a reinforced concrete structure, the fire would have had to burn long and hot to impact the steel (within),” she said Thursday night. “Once the temperature gets about one-third to half the temperature of the melting point of steel that’s when you start to see more significant decreases” in its stability.

Once safety officials are sure that the site is safe and the fire is out, inspectors will be sent in, she said. Then structural engineers can do analysis to understand what happened and how the remaining structure was impacted and what kind of repairs will be needed.

So how long could all of that take? It’s too soon to tell, she said.

The collapse gridlocked traffic for miles and forced motorists to turn back — if they were able to move at all.

Alternate Routes to Get You Around I-85 Bridge Collapse

Brookhaven resident Justin Harrison, 36, said his girlfriend was picked up by a Lyft driver from Hartsfield-Jackson International Airport at 5:30 p.m. At 9 p.m., she was still stuck in traffic.

“I’m sitting in my car waiting for you,” he told her. “If there’s anywhere you can stop, I can pick you up.”

“She’s cool,” Harrison said despite the delay.

Harrison praised Atlanta police for their response to the collapse.

“It’s amazing what the city has done so fast to respond,” he said.

Michael Brooks, 43, was heading home on I-85 when he saw the smoke.

“I thought it was a terrible wreck. Vehicles stopped suddenly,” said Brooks who works at CNN. People started getting out of their cars. They said, “the bridge is going to collapse.” Brooks said he sat there for two and a half hours.

As for tomorrow, he said about getting to work, “I guess I’ll figure that out some way.”

Anne Marsden was leaving her office on Ottley Drive next to the Sweetwater Brewery around 6:30 p.m. when she saw the smoke coming from the interstate.

Anne Marsden took this photo while passing by Piedmont Road before the fire engulfed the bridge and caused it to collapse.
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“It was a mess,” said Marsden, who runs a marketing business. “Nothing was moving.”

She said firefighters were spraying water on a nearby apartment complex to keep the fire from spreading.

She used an alternative route to get to her Buckhead home, but stopped at Houstons on Piedmont to check on several employees who'd gone there. That's when the bridge collapsed.

“Now we are in planning mode via text for how to do business with no access to our office for an unknown period of time,” she said.

Hours after the bridge failed, the air stretching a quarter mile north of the collapsed bridge was still acrid, spreading like a thin black fog.

All businesses surrounding the site were closed including Tower Liquors, several popular adult entertainment clubs, shops and restaurants. The collapse site is near the Orkin pesticide corporate headquarters on Piedmont Road.

The collapse of a major interstate through town is sure to scramble commerce. Companies are contemplating their next moves.

A spokeswoman for Atlanta-based delivery giant UPS said the company’s contingency planners are assessing the I-85 situation “to define our activity, routing.”

Equifax said its headquarters in Midtown Atlanta will be open Friday, but “we are advising employees to work remotely… to avoid traffic congestion.” The company plans to have more internal discussions in coming days “as more information is known in terms of expected time for repairs,” according to Equifax spokeswoman Ines Gutzmer.

While many interstate tractor trailer drivers use I-285, rather than taking I-85 through the city, the closing of I-85 will push traffic onto other interstates, potentially hindering traffic there.

“It’s a massive productivity issue,” said Brian McGowan, a former CEO of Atlanta’s economic development arm and now a principal in the US Public Policy and Regulation practice at law firm Dentons. “You are going to have hundreds or thousands of companies who can’t get their employees to work on time.”

» WATCH AND LISTEN: Driver passes by I-85 fire

The public sector will also take a blow as tens of thousands of government workers also will be affected.

The City of Atlanta Government Offices will have a delayed start of 10:00 a.m. on Friday. And the Municipal Court of Atlanta will also have a delayed start of 10:00 a.m.

McGowan said the short-term potential losses are substantial. It will disrupt businesses’ supply chains. Families will have to re-think how they travel around the city.

The collapse of the bridge will shift sales at restaurants as diners choose other places to eat because of convenience.

And like the infamous Snowjam debacle of 2014, McGowan said, “it once again highlights the vulnerability of the Atlanta transportation system.”