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3 arrested in connection with fire that collapsed I-85 bridge in Atlanta

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ATLANTA – Three people are in custody after a fire that led to the Interstate 85 bridge collapse in Atlanta.

Three people were arrested Friday night in connection with the blaze, the Atlanta Fire Rescue Department said. Authorities believe one of the suspects started the fire intentionally.

Citing the state fire marshal's office, Atlanta's WSB-TV reports that one man has been charged with criminal damage to property and two others with criminal trespass.

The fire started Thursday evening under an I-85 overpass in north-central Atlanta, north of the highway's split with I-75. It grew into a massive fireball, sending thick smoke onto the highway above.

Firefighters responded, but the fire weakened the structure, causing the northbound section to fall and severely damaging the southbound side. No one was injured, and officials said they didn't immediately know what caused the fire.

Here's what we know about what led to it:

Started in a construction-supplies storage area

The flames ignited in a fenced-in area where the state stores construction materials and supplies near the overpass, state Department of Transportation Commissioner Russell McMurry said.

Gov. Nathan Deal said Thursday that he had heard speculation it was caused by some "PVC products that caught fire."

McMurry initially said the materials stored under the highway were PVC pipes, but later said they were HDPE -- high-density polyethylene -- pipes. He said the conduits are used in the "traffic management, cabling, fiber-optic and wire network."

The material had been stored there "for some time, probably since 2006 or -7," McMurry said.

"We're as eager to learn the cause of this fire as anyone," McMurry said.

Drivers in one of the nation’s most congested cities faced a jarring new reality Friday as they were forced to game out how to get around a collapsed portion of Atlanta’s Interstate 85 — one of the Southeast’s major north-south arteries.

The shutdown likely sets the city up for traffic headaches for months after creating navigation hell Thursday with jams that extended five miles or more and stranded motorists for hours.

The closure comes at a sensitive time for a city accustomed to gridlock — with hordes of spring break vacationers poised to drive though the regional hub and the Atlanta Braves set to play a preseason game Friday night in their new stadium northwest of the city.

“I think it’s as serious a transportation crisis as we could have,” Atlanta Mayor Kasim Reed said Thursday evening.

CNN contributed to this report.