PHILADELPHIA: Human remains were recovered on Monday from a fallen overpass on Interstate 95 in Philadelphia as crews removed concrete debris from the site of a fiery weekend highway collapse that closed a stretch of one of the busiest traffic corridors along the U.S. East Coast.

The section of I-95 was shut down in both directions after a tanker truck hauling gasoline caught fire on Sunday, causing the concrete to buckle and collapse. Authorities have not said precisely how the fuel was ignited.

As excavation teams labored to clear rubble from the site on Monday, a body was recovered from the wreckage and turned over to the Philadelphia County Medical Examiner for identification, state police said in a statement.

The truck driver, Nathaniel Moody, had been unaccounted for in the immediate aftermath of the accident, local ABC affiliate WPVI-TV reported.

During the morning commute, local traffic reporters said bumper-to-bumper traffic was spotted near the collapse and along alternate routes, but it appeared that some motorists heeded the warnings to take public transportation or stay home.

"Things are obviously getting worse moving into the heart of rush hour," KYW News Radio traffic reporter Justin Drabick said around 8 a.m. EST (1200 GMT).

He noted that Mondays were typically a light traffic day. "Tomorrow is really going to be the true test."

Workers and investigators spent the morning and early afternoon surveying the damage at the scene as an excavator clawed through the rubble and moved massive pieces of concrete where the section of highway once stood.

Officials said it would take several months to rebuild the segment of I-95, the main north-south highway along the East Coast, running from Miami to the Canadian border in Maine.

U.S. Transportation Secretary Pete Buttigieg said the federal government was working with the state of Pennsylvania to restore the highway.

"This is going to be a major disruption in that region," Buttigieg said. He did not specify a precise timetable for a fix but said "definitely not days. I mean if it is weeks we're not talking about a couple."

The chief of the Federal Highway Administration plans to visit the site, White House spokesperson Karine Jean-Pierre said. The U.S. National Transportation Safety Board (NTSB) is investigating.

Pennsylvania Governor Josh Shapiro issued a disaster declaration on Monday, freeing up federal funds to help in the rebuild the portion of a highway that is used by 160,000 vehicles daily.

He also urged residents to look for alternate routes, to take commuter trains or to work from home.

Delivery companies UPS UPS.N and FedEx FDX.N said they were making adjustments.

Buttigieg said the department planned to use emergency relief funding to help with the rebuilding but did not specify an amount.

The closed section of I-95 is a major route to distribute goods, he said. "This is not just about commutes — this is also supply chain."

Andy Herrmann, a past president of the American Society of Civil Engineers, said bridges are not designed to withstand the heat from a tanker truck fire, which could be upward of 2,000 Fahrenheit (1,090 Celsius), and that such incidents were not common.

Herrmann said Sunday's collapse might prompt discussion about changing bridge design requirements, but it was difficult to see how the U.S. could afford to upgrade the many overpasses in the country.

"I mean, they're looking to maintain the basic safety of the bridges due to deterioration," he said.