Traffic barely moves in a neighborhood near an elevated section of Interstate 95 that collapsed in Philadelphia, on Monday. Matt Rourke/Associated Press

An overpass on Interstate 95 that collapsed in North Philadelphia on Sunday will take months to replace, officials said, snarling a bustling East Coast corridor during the summer travel season and severing a main commercial artery for the city.

Standing before the wreckage of what he called “remarkable devastation,” Pennsylvania Gov. Josh Shapiro, a Democrat, and other officials warned motorists to expect detours and embrace public transit for an unknown period as the highway is rebuilt. Traffic during the Monday morning commute moved slowly on nearby streets as drivers tested new routes around the closed highway.

A northbound slice of the road cratered and the southbound expanse is structurally unsound after a tanker carrying gasoline went up in flames under the overpass early Sunday morning, shooting out apocalyptic plumes of smoke and burning with such searing force that steel girders under the highway appear to have melted.

“I found myself, you know, thanking the Lord that no motorists who were on I-95 were injured or died,” Shapiro said, after announcing plans to declare a state of emergency to secure federal assistance.

Officials could not say what caused the fire that collapsed the roadway, which carries about 160,000 vehicles a day — a combination of through-traffic and local activity across the nation’s sixth-most-populous city and surrounding suburbs. The circumstances of the crash are being investigated by multiple agencies, including the National Transportation Safety Board.

The conditions to create such a calamity are so rare that highway bridges aren’t typically built to be fireproof like buildings, said a Drexel University engineering expert.

“We don’t design them for fire resistance because we don’t expect to have any types of fire incidents,” said Amir Farnam, who studies reinforced-concrete infrastructure and estimated that it would take temperatures of 500 degrees Celsius to cut the steel used in highway girders in half.

A minute after the blaze was reported to emergency responders, Tara Hallinan, 30, found herself faced with a wall of bright orange flames.

She pulled out her phone in the back seat of a Lyft and captured the crackling fire and plumes of black smoke engulfing the interstate.

This screen grab from video provided by WPVI-TV/6ABC shows the collapsed section of I-95 with fire trucks on the scene in Philadelphia on Sunday. WPVI-TV/6ABC via AP

“There were flames on either side of us,” said Hallinan, who was on her way to work at a hotel in Old City. “It’s going to be a big hassle for Philadelphians that take the 95. I’m not really sure what they’re going to do.”

Anxiety was overcome by weary acceptance among residents reached by phone Sunday, who said they had no choice but to wait and see what their leaders would do. Some recalled disruptions caused in 1996, when a fire burned for nearly five hours under a stretch of the same highway in the city, collapsing a span of interstate that required more than a week of detours and about six months of reconstruction.

It took hours Sunday for emergency response and transportation officials to establish detours as they closed streets surrounding the collapse along a stretch of Northeast Philadelphia.

The closure – between Exit 32 for Academy Road and Linden Avenue and Exit 30 for Cottman Avenue and Rhawn Street — impacts a mostly residential slice of the city home to the Bustleton and Tacony neighborhoods, which were settled by Irish, Italian and German immigrants but now bustle with a racially diverse population of Indians, Russians, and other immigrant families and store owners.

Mike Ditro, the manager of Curran’s Irish Inn, adjacent to I-95 on Cottman Avenue, said he could see the smoke from work.

Ditro, 55, said that he won’t be able to know the true toll of the collapse until Monday but that a police officer was helping drivers navigate the area as traffic was affected near the restaurant.

“There’s nothing you can do,” he said. “It’s going to be gridlock, I’m sure.”

Trash collection and bus service would be disrupted, officials warned Sunday. Philadelphia’s schools superintendent issued a statement saying students and staff members with commutes disrupted by the closure would be excused for arriving late.

Firefighters stand near the collapsed part of I-95 in Philadelphia on Sunday. Office of Emergency Management via Associated Press

The collapse set off a wave of concern that echoed from City Hall all the way to the White House, where President Biden was briefed.

Transportation Secretary Pete Buttigieg pledged the support of the Transportation Department and said the Federal Highway Administration is working with adjacent states to alert drivers about the collapse and assist with traffic plans. He urged travelers planning to cross through the region to pay close attention to local traffic alerts as “we expect significant regional impact,” he said in a tweet.

I-95, a major north-south artery that carries freight and goods from Maine to Florida, functions as a key connection to other primary highways including the New Jersey Turnpike or Interstate 295, which splits off in Delaware to carry travelers passing through the region around Philadelphia as they continue up and down the Eastern Seaboard.

City and state transportation officials continue to work to come up with traffic plans and alternatives to help locals who rely on the highway, which is not passable.

Detours on Sunday included Route 63 West (Woodhaven Road), U.S. 1 South, Interstate 76 East and Interstate 676 East for southbound I-95. Instead of northbound I-95, the city recommended that motorists use I-676 West, I-76 West, U.S. 1 North to Route 63 East (Woodhaven Road).

Transit officials with the Southeastern Pennsylvania Transportation Authority said they would increase train service starting this week as an alternative.

Shapiro on Sunday could not give a timetable for rebuilding, saying that engineers must assess the damage but that the work will “take some number of months.”

The fire was reported at 6:20 a.m., with Philadelphia firefighters arriving on scene at the Cottman Avenue exit about 10 minutes later. It took about an hour for them to get the blaze under control, the Philadelphia Fire Department said in a tweet, and personnel were expected to remain overnight to monitor the spill for new fires.

The tanker was carrying as much as 8,500 gallons of gasoline, some of which spilled into a drainage system that ends in the nearby Delaware River, where the U.S. Coast Guard used a floating barrier known as a boom to contain the spillage.

Smoke rises from the scene following a collapse on I-95 after a truck fire, on Sunday in Philadelphia. Philadelphia Fire Department via Associated Press

Shapiro said he only saw a light sheen of fuel on the water from the tanker spill, an assessment backed up by the Coast Guard.

“It hasn’t made its way to the water that much,” said Ensign Josh Ledoux, a spokesperson for the Delaware Bay sector of the Coast Guard, which continues to monitor the spill.

At least one car remains under the rubble, Shapiro said. The identity and status of the tanker driver remains unclear.

An alphabet soup of agencies responded to assess the damage as residents and business owners watched smoke climb into the sky all morning, trying to take the emergency in stride – as is expected in a city known for its tough reputation.

As she looked ahead to a tough commute, Monica Hawk, 44, created a playlist on Apple Music to cope with the disruptions that she expects will extend her drive time to nearly two hours.

On deck are hits from Miley Cyrus, Lizzo and One Direction, including the aptly titled “Story of My Life.”

“It’s going to be a while,” said Hawk, the interim chief executive of One Bright Ray Community High School. “We’re just going to be patient.”

At Joe Santucci’s Square Pizza on Woodhaven Road, delivery drivers avoided their usual I-95 routes – bringing customers their pizzas 20 or 30 minutes later than usual.

“Everybody in the neighborhood right now is waiting to find out what the city is going to do and when 95 will be back up and running,” said Jessica Chiffens, a manager.

Tired of watching an endless loop of fiery scenes from the interstate, customers at the bar finally asked the staff to change the channel to baseball, to watch the Phillies take on the Los Angeles Dodgers.

It was a home game, and the Phillies delivered a 7-3 victory for a city in need of a win.