What We Know About the I-95 Collapse in Philadelphia

A section of I-95 in Philadelphia collapsed on Sunday after a fiery crash involving a tanker loaded with gasoline. Officials warned that it could take months to replace the elevated stretch of road, further complicating traffic problems in one of the nation’s largest cities this summer.

The crash on I-95, which runs the length of the East Coast from Maine to South Florida, left a section of the northbound side of the highway in a heap of ruins and the southbound section so badly damaged that it will be demolished this week.

The authorities have cautioned that the investigations into the crash and the collapse of the overpass are only just beginning, but here is what we know so far.

The authorities believe the driver lost control of the tanker.

Pennsylvania officials said the driver was heading northbound on I-95 early Sunday and lost control while negotiating the left-hand curve of an off-ramp in northeast Philadelphia.

The truck, which was hauling about 8,500 gallons of gasoline, “landed on its side and ruptured the tank and ignited the fire,” Pennsylvanias’s transportation secretary, Mike Carroll, said at a news conference on Monday.

A team of investigators from the National Transportation Safety Board arrived in Philadelphia on Sunday and were expected to issue a preliminary report in two to three weeks.

The driver is feared to have died in the crash.

The Pennsylvania State Police announced on Monday afternoon that a body had been found in the debris, but that the authorities were still in the process of identifying the remains.

Family members of Nathan Moody, a 53-year-old truck driver who lived in New Jersey and delivered fuel to gas stations in the area, said the police had contacted them, seeking dental records.

The intensity of the fire most likely caused the collapse.

Mr. Carroll said there were no concerns about the bridge before the accident, describing it as structurally sound and about 10 to 12 years old. Officials and structural engineers have said that the heat generated by the fire, which lasted about an hour, could have melted or weakened the steel beams supporting the overpass.

Professor Abi Aghayere of Drexel University told The Associated Press that bridges like this did not typically have fire protection, like concrete casing.

A southbound section of the road was also damaged, and efforts to demolish it were to begin as soon as Monday.

Fixing this section of the interstate could take months.

This stretch of the highway, in northeast Philadelphia near the Delaware River, is used by about 160,000 vehicles a day, officials said. But much of the interstate traffic traveling through the region already bypasses Philadelphia using the New Jersey Turnpike, which runs roughly parallel to I-95 east of the river and becomes I-95 farther north, on the way to New York City.

Gov. Josh Shapiro of Pennsylvania said in a news conference on Sunday that he expected the repairing of the damaged section of the interstate to take months.

The repair of other highways that suffered similar damage in the past took several weeks, said Thomas Gernay, an assistant professor of engineering at Johns Hopkins University.

“We are in an unlucky situation where the fire occurs just underneath a structure,” he said.

Officials have added extra cars to commuter trains, arranged detours and offered free parking at some mass transit lots, but traffic was still a problem on Monday.

“We’d ask people to have patience,” Mr. Carroll, the transportation secretary, said.

Jon Hurdle, Campbell Robertson and Amanda Holpuch contributed reporting.