A fire caused an overpass on one of America's busiest highways to collapse early Sunday in Philadelphia, authorities said, as reports attributed the cause to a truck that burst into flames under the bridge.
The collapse took out four traffic lanes along an elevated section of heavily traveled Interstate 95, though no injuries were immediately reported.
"Companies arrived on location and they found... heavy fire from a vehicle -- we don't know what type of vehicle it was," Captain Derrick Bowmer, of the Philadelphia Fire Department, told a news conference.
Bowmer added the situation was considered a hazmat incident, but could not confirm reports that the burning vehicle was an oil tanker.
Federal and local law enforcement are looking for the driver, whose whereabouts are unknown, local media reported.
The north-south highway -- one of the busiest in the United States, connecting major cities along the East Coast from Maine to Florida -- remains closed in both directions in the Philadelphia area, officials said.
Rebuilding the section of destroyed highway could take weeks, authorities said, a nightmare scenario for commuters as well as for road travelers at the start of the summer holiday season.
"Avoid area. Plan and seek alternative travel routes," the Philadelphia Office of Emergency Management said in a tweet.
U.S. Secretary of Transportation Pete Buttigieg said on Twitter he is offering "any assistance that USDOT can provide to help with recovery and reconstruction."
Television images showed flames and billowing smoke coming from the crumbled section of I-95 in the northeastern city's Tacony neighborhood, with parts of the elevated roadway having fallen onto the lanes below.
City authorities issued a series of alerts on Twitter about a tanker truck fire on the highway, which local media reported caught fire underneath the bridge, apparently causing the collapse.
A city spokeswoman told AFP that a "large fire under I-95" caused the highway to collapse, but did not attribute it to any vehicle. She said the fire has been declared "under control."
Local media reported the fire started around 6:20 am (0220 GMT), when Sunday traffic is typically light.
"I will always be grateful to our first responders for the dangerous, life-saving work they do to keep residents and visitors safe," Philadelphia Mayor Jim Kenney said on Twitter.
The southbound lanes of the highway, while still standing, are "compromised," Bowmer said. "They got a lot of heat and heavy fire."
"I-95 will be impacted for a long time, for a long time," city Managing Director Tumar Alexander told a news conference, according to The Philadelphia Inquirer.
Residents told city media outlets that they heard several explosions, which a fire department captain told the local NBC station were coming from underground, caused by runoff from the truck.
