Christopher Buchanan, Sean Rossman

WXIA-TV, Atlanta, USA TODAY

ATLANTA — Atlanta area residents will have to get used to the absence of one of the city's main traffic arteries after officials said it will take "at least several months" to rebuild a portion of a bridge that collapsed on Interstate 85 on Thursday.

Georgia Department of Transportation Commissioner Russell McMurry said hundreds of feet of both the north and southbound parts of the bridge will need to be replaced. Demolition has started and will continue into Monday. The planning for a replacement bridge already is underway. However, McMurry said, the process will take time.

“The big question on everyone’s mind is how long will this take to repair?” he asked. “We’re not able to give you a firm estimate at this moment but you should know that this will at least several months to get this rebuilt.”

McMurry said U.S. Transportation Secretary Elaine Chao authorized $10 million dollars to pay to replace the bridge.

Authorities arrested three people Friday in connection with the fire, WXIA-TV and the Atlanta Journal-Constitution reported. The three were identified as: Basil Eleby, who was charged with criminal damage to property, Sophia Bruner, who was charged with criminal trespass, and Barry Thomas, also charged with criminal trespass.

Authorities said they believe the three are homeless and were living in the vicinity of where the fire took place.

McMurry said authorities still do not know the cause of the fire that erupted about 6 p.m. Thursday and led to the northbound bridge collapsing. The area where the fire originated, he said, was storage for high-density plastic conduit used for cabling and fiber optics. He said the material isn't combustible.

Georgia Gov. Nathan Deal declared a state of emergency and hinted the road ahead could be long. The highway carries 250,000 cars a day.

"Despite our coordinated efforts, this will be a long process," he said after meeting with federal and state transportation officials. "This is due, in part, to the fact that bridge beams must be cast, poured, tested, transported and individually installed. During this time, public safety is our chief priority and primary concern."

In the meantime, residents may have to rely on mass transit to get around. Atlanta officials encouraged commuters to consider using the Metropolitan Atlanta Rapid Transit Authority, or MARTA, to get around.

Atlanta Mayor Kasim Reed said city officials will look back to the 1996 Olympics' plans to help determine the best way to handle the traffic situation in the coming weeks.

"We actually handled the Olympics very nicely in Atlanta and I really think that is the closest comparison from a traffic standpoint with what we're going to be going through over the next four to six weeks," Reed said.

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"MARTA is providing additional services to accommodate the expected influx of passengers needing to navigate traffic congestion and delay," MARTA spokesman Erik Burton said in a series of emails. "MARTA continues to work closely with our state and local partners to ensure that residents and visitors can safely reach their destinations."

MARTA promised increased rail services and additional representatives, but did not release specific train schedules before the Friday morning rush hour.

"We will have to continue to evaluate the situation and adjust as we do," McMurry said. "This incident — make no bones about it — will have a tremendous impact on travel."

The interstate is a major artery for the U.S. South and a thoroughfare for traffic heading north and south through Atlanta. The bridge collapse effectively "puts a cork in the bottle," said Georgia State Patrol Commissioner Mark McDonough.

The fire erupted about 6:30 p.m. and the northbound lanes collapsed about 7 p.m. Despite the destruction of the roadway, no injuries were reported Sgt. Cortez Stafford with Atlanta Fire Rescue said.

Reed said city officials spoke with the FBI and "there is no evidence that this is related to terrorism."

"It's going to take some time to do a thorough assessment to determine what damage has been done to that section of the interstate," Reed said.

Georgia has hundreds of structurally deficient bridges, according to the American Road and Transportation and Transportation Builders Association. However, the I-85 bridge that collapsed was considered sound.

Some state and city agencies delayed the opening of their offices until 10 a.m. ET on Friday.

The Atlanta Public Schools planned to open on time, while DeKalb County Schools would not open.

Contributing: Julie Wolfe, WXIA-TV, Atlanta; The Associated Press. Follow Christopher Buchanan on Twitter: @ChrispyBuc