Cars getting off at an exit for 400 started slowing more quickly than a normal rate and some cars pulled off onto the shoulder.
Atlanta Mayor Kasim Reed said the collapse is not related to terrorism.
Traffic backs up across Interstate 85 in Atlanta during a massive fire.
A section of US Interstate 85 in north Atlanta collapsed Thursday after a massive fire, local officials confirmed.
Flames and smoke engulf a section of Interstate 85 in Atlanta. The cause of the fire was not immediately known.
The fire was still being attended to Thursday night. The crash trucks from the airport would spray foam on the fire and the flames would subside, only to flare up again.
All five lanes of the highway in each direction were blocked and will be closed for the foreseeable future, officials said.
Crews work to put out the remaining fire under I85 in Atlanta.