Traffic was backed up for miles in Atlanta after part of Interstate 85 collapsed due to a massive fire.

Witnesses say troopers told motorists to turn around on the bridge because they were concerned about its integrity.

ATLANTA (CNN) - A major question remained Friday in the hours after a fire caused the collapse of a section of Interstate 85 in Atlanta: What caused the flames? Traffic will be directed from that major road to other interstates, including those flanking the stadium.

A man has been arrested on suspicion of intentionally setting a huge fire that brought down part of an elevated interstate highway in Atlanta, a collapse that is expected to complicate traffic for months in one of the nation's most congested cities. Both Thomas and the woman were charged with criminal trespass, according to Georgia Deputy Insurance Commissioner Jay Florence.

Fire department spokesman Sgt. Cortez Stafford told the Atlanta Journal-Constitution ( ) that the fire was under control Thursday night. But traffic was a nightmare, with drivers lined up bumper-to-bumper on nearby streets.

Paul Pagnato, wearing a Yankees cap, flew to Atlanta from Virginia for the game and said the drive from the airport south of Atlanta "wasn't bad". As of 9:41 p.m., Stafford said that the fire had been contained.

Knowles said he drove less-traveled roads "because I knew how the interstate was going to be".

Amelia Ford picked a new route to work by vehicle 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 officials say repairing damaged sections of I-85 north of downtown Atlanta will take months.

U.S. Senator Rubio - Hackers targeted former presidential campaign staffers
Mark Warner, D-Va. meet with reporters on Capitol Hill in Washington , Wednesday, March 29, 2017, to discuss the comm. He would not comment on that information, other than saying it would be reflected in the committee report.

"We're trying to determine everything we can about how quickly can we fix it and get it back in service", Deal said.

"The Georgia Department of Transportation (GDOT) 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".

The flames ignited in an area where the state stores construction materials and supplies near the overpass, state Department of Transportation chief Russell McMurry said. Authorities were still working to determine how the fire started.

He said the material was a high-density plastic conduit used for cabling and fiber optic wire networks.

The fire also caused a section of freeway to collapse.

He says firefighting crews noticed chunks of concrete beginning to drop Thursday as they were fighting the fire under the bridge and got out of the way minutes before it collapsed.

Metropolitan Atlanta Rapid Transit Authority (MARTA) has issued a statement of their own. Local officials confirmed that $10 million in federal funds have been released to help pay for the fix and reconstruction of I-85 damaged by the collapse. We're not able to give you a firm estimate.

Built in 1953 and renovated in 1985, the span scored high in its most recent inspection, receiving a rating of 94.6 out of 100 in 2015, said Natalie Dale, a spokeswoman for the Georgia Transportation Department.

Structural engineering experts said fires on highways and bridges rarely burn long enough or hot enough to cause a complete collapse.