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Three people were arrested Friday in connection with a raging fire that caused part of Interstate 85 in Atlanta to collapse, shutting down one of the busiest stretches of roadway in America, the state fire marshal's office said.

Authorities believe the three are homeless and were at the scene when the fire broke out Thursday, according to Glenn Allen, a spokesman for Georgia’s Office of Insurance and Safety Fire Commissioner.

Two of them — Sophia Bruner and Barry Thomas — were charged with criminal trespass, while a third — Basil Eleby — was charged with criminal damage to property, Allen said. Allen told NBC station WXIA in Atlanta Eleby is believed to have started the fire. Atlanta Fire Rescue said more charges could be added as the investigation progresses.

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Bridge inspectors were assessing damage as officials worked to unsnarl traffic. Rebuilding could take months.

"This is about as serious a transportation crisis as we can imagine," Mayor Kasim Reed said late Thursday.

Three northbound and three southbound sections of the highway will need to be replaced, according to Russell R. McMurry, the commissioner of the Georgia Department of Transportation. It could take months to rebuild, McMurry said.

"That is no small feat, but we're up to the challenge," McMurry said.

The massive fire was reported at 6:21 p.m. ET underneath the bridge on the northbound side — near where the interstate merges with another key artery, State Highway 400 — forcing authorities to close the interstate and turn drivers around during rush hour.

At about 7 p.m., the bridge gave way in a flaming heap that spewed thick, black smoke high into the air.

A firefighter surveys the section of an overpass that collapsed from a large fire on Interstate 85 in Atlanta on March 30, 2017. David Goldman / AP

McMurry on Friday said the blaze started in an area used as a "storage location" for "surplus construction materials," such as polyvinyl chloride (PVC) piping, a material commonly used in construction. Gov. Nathan Deal suggested Thursday night that the PVC may have ignited for some reason.

No one was injured in the collapse, authorities said Friday. But traffic was a nightmare, with drivers lined up bumper-to-bumper on nearby streets. State and local officials said more than 225,000 vehicles travel through the affected area on an average weekday.