PHILADELPHIA (AP) — An elevated section of Interstate 95 collapsed early Sunday in Philadelphia after a tanker truck carrying flammable cargo caught fire, closing a heavily traveled segment of the East Coast’s main north-south highway indefinitely, authorities said.

Transportation officials warned of extensive delays and street closures and urged drivers to avoid the area in the northeast corner of the city. Officials said the tanker contained a petroleum product that may have been hundreds of gallons of gasoline. The fire was reported to be under control.

Video from the scene showed a massive concrete slab had fallen from I-95 onto the road below. There were no reports of injuries.

The northbound lanes of I-95 were gone, and the southbound lanes were “compromised” due to heat from the fire, said Derek Bowmer, battalion chief of the Philadelphia Fire Department. Runoff from the fire or perhaps broken gas lines were causing explosions underground, he added.

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The Maryland State Highway Administration said on Twitter, “Major bridge out in both directions on I-95 in Philadelphia. Motorists planning to travel north from Maryland should plan alternate routes.”

“While this took place outside of Maryland, it could impact your travel if you are headed toward the Philadelphia area or planning to use I95. Stay safe.”

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Some kind of crash happened on a ramp underneath northbound I-95 around 6:15 a.m. The northbound section above the fire collapsed quickly, state Transportation Department spokesman Brad Rudolph said.

Mark Fusetti, a retired Philadelphia police sergeant, said he was driving south toward the city’s airport when he noticed thick, black smoke rising over the highway. As he passed the fire, the road beneath began to “dip,” creating a noticeable depression that was visible in video he took of the scene, he said.

He saw traffic in his rearview mirror come to a halt. Soon after, the northbound lanes of the highway crumbled.

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“It was crazy timing,” Fusetti said. “For it to buckle and collapse that quickly, it’s pretty remarkable.”

Officials work on the scene following a collapse on I-95 after a truck fire, Sunday, June 11, 2023 in Philadelphia. (Joe Lamberti/AP)

The southbound lanes were heavily damaged, “and we are assessing that now,” Rudolph said Sunday afternoon.

The collapsed section of I-95 was part of a $212 million reconstruction project that wrapped up four years ago, Rudolph said. There was no immediate time frame for reopening the highway, but officials would consider “a fill-in situation or a temporary structure” to accelerate the effort, he said.

Motorists were sent on a 43-mile detour, which was going “better than it would do on a weekday,” Rudolph said. “The fact that the collapse happened on a Sunday helped ease congestion.”

He expected traffic “to back up significantly on all the detour areas.”

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White House press secretary Karine Jean-Pierre said in a Twitter post that President Joe Biden was briefed on the collapse and that White House officials were in contact with Pennsylvania Gov. Josh Shapiro and Philadelphia Mayor Jim Kenney’s offices to offer assistance.

“This is a major artery for people and goods, and the closure will have significant impacts on the city and region until reconstruction and recovery are complete,” Transportation Secretary Pete Buttigieg said in a social media post.

The National Transportation Safety Board said it was sending a team to investigate the fire and collapse.

CBS Philadelphia reported Sunday morning that a two-mile radius of the roadway was closed from Exit 25, just south of the Betsy Ross Bridge in Philadelphia, north to Exit 32. Northbound travelers on I-95 can still use the Betsy Ross Bridge exit, but motorists can’t use it to get onto I-95. The news station was advising Philadelphia-area motorists to take Route 1 to get around the closure, and said that New Jersey-bound travelers could use U.S. 130 or Interstate 295.

Most drivers traveling the I-95 corridor between Delaware and New York City use the New Jersey Turnpike rather than the segment of interstate where the collapse occurred. Until 2018, drivers did not have a direct highway connection between I-95 in Pennsylvania and I-95 in New Jersey. They had to use a few miles of surface roads, with traffic lights, to get from one to the other.

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Officials were also concerned about the environmental effects of runoff into the nearby Delaware River.

After a sheen was seen in the Delaware River near the collapse site, the Coast Guard deployed a boom to contain the material. Ensign Josh Ledoux said the tanker had a capacity of 8,500 gallons, but the contents did not appear to be spreading into the environment.

“As far as waterways go, it’s being contained, and it seems like things are under control,” he said.

Thousands of tons of steel and concrete were piled atop the site of the fire, and heavy construction equipment would be required to start to remove the debris, said Dominick Mireles, director of Philadelphia’s Office of Emergency Management.

The fire was strikingly similar to another blaze in Philadelphia in March 1996, when an illegal tire dump under I-95 caught fire, melting guard rails and buckling the pavement.

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The highway was closed for several weeks, and partial closures lasted for six months. Seven teenagers were charged with arson. The dump’s owner was sentenced to seven to 14 years in prison and ordered to pay $3 million of the $6.5 million repair costs, The Philadelphia Inquirer reported.

More recently in Atlanta, an elevated portion of Interstate 85 collapsed in a fire, shutting down the heavily traveled route through the heart of the city in March 2017. A homeless man was accused of starting the blaze, but federal investigators said in a report that the state transportation department’s practice of storing combustible construction materials under the highway increased the risk of fire.

Associated Press writers Mark Scolforo in Harrisburg, Pennsylvania, and Jake Offenhartz in New York and Banner staff contributed to this report.