An elevated section of Philadelphia’s Interstate 95 collapsed on Sunday after a tanker truck carrying flammable cargo caught fire.
The heavily travelled segment of the major highway on America’s East Coast has been closed indefinitely following the disaster, authorities said.
The fire is understood to have been caused by a crash on a ramp underneath the northbound I-95 around 6.15 am on Sunday, while the section of road above the blaze collapsed quickly.
The tanker involved in the fire contained a petroleum product, which may have been hundreds of gallons of gasoline, officials said. The fire took around an hour to get under control.
There were no initial reports of injuries, but Governor of Pennsylvania Josh Shapiro said at least one vehicle was still trapped beneath the collapsed road.
“We’re still working to identify any individual or individuals who may have been caught in the fire and the collapse,” he said.
Photos and footage from the scene showed a massive concrete slab had fallen from I-95 onto the road below. Mr Shapiro said his flight over the area showed “just remarkable devastation”, and said a complete rebuild would take “some number of months”.
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, and soon after the northbound lanes of the highway crumbled.
“It was crazy timing,” Mr Fusetti said. “For it to buckle and collapse that quickly, it’s pretty remarkable.”
The southbound lanes of I-95 did not collapse but were “compromised” by heat from the fire, said Philadelphia Fire Department.
The affected section was part of a $212 million (£167m) reconstruction project that finished four years ago.
Pennsylvania Transportation Secretary Michael Carroll said the I-95 segment carries around 160,000 vehicles per day and was likely the busiest interstate in Pennsylvania.
Work continued throughout Sunday night to remove the collapsed section, while the US National Transportation Safety Board said it was sending a team to investigate the fire and collapse.
Officials were also initially 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. Experts later said the tanker’s contents did not appear to be spreading into the environment.
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.
