Updated at 2 p.m. ET.

Transportation officials in Georgia are scrambling to cope with a crisis, after a huge fire caused a bridge on Interstate 85 to collapse in Atlanta on Thursday night.

Gov. Nathan Deal has declared a state of emergency, and with the heavily used road closed in both directions, drivers are being told to find other options — from detours to mass transit.

The shutdown affects a roughly 3-mile portion of I-85, blocking a major artery that runs through the heart of Atlanta. Friday morning, officials said they don't yet know what caused the fire. In an update around midday, they said repairs will likely take "several months."

Officials say no injuries were reported as a result of the fire. Police had cleared the interstate before part of the overpass failed catastrophically.

The road normally carries some 250,000 vehicles a day. While the collapse took out northbound lanes of I-85, officials say damage to the southbound lanes must also be repaired before they can be reopened.

Mark McDonough, commissioner of the Georgia State Patrol's Department of Public Safety, is asking drivers to be patient, as member station WABE reports. But he acknowledges that other highways will be "slammed" with traffic.

"It's going to take a while for everybody to adjust to this — what is the new normal?" McDonough said. "We're going to find out over the next couple of weeks."

In addition to complicating daily commutes and deliveries through the heavily populated north-central portion of Atlanta, the interstate closure stands to complicate the plans of drivers that range from spring break tourists to fans of the Atlanta Braves — which is hosting the first-ever exhibition baseball game in its new ballpark Friday night.

The Braves' new stadium sits at the intersection of I-285 — Atlanta's perimeter loop that will be used as a detour during repairs — and I-75. It's about 10 miles northwest of the closures that begin at the spot where I-75 and I-85 join.

As of Friday morning, hot spots from the fire were still preventing crews from assessing the full extent of the damage. Repairs are "expected to be a time-consuming event," Georgia DOT Commissioner Russell R. McMurry said Friday morning.

WABE's Lisa George tells NPR's Newscast unit, "What appear to have been plastic pipes stored under the highway caught fire; no one knows how yet. They burned for about an hour, sending black smoke into the air — and then the northbound lane of the interstate just fell. "

George also spoke to a nearby resident, Elizabeth Gaston, who lives in an apartment building next to the overpass.

Gaston says she saw a "bunch of fire coming out, shooting out from under the underpass and all up over the bridge. And then, [after] a couple of minutes, all of a sudden you heard just 'boom.' And I guess that was when the, 85 collapsed. It was pretty scary."

The fire struck a spot used to store construction supplies. The DOT's McMurry called it "a secured area containing materials such as PVC piping, which is a stable, non-combustible material."

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