By Jarrett Renshaw

PHILADELPHIA (Reuters) -Philadelphia residents were bracing for a brutal morning commute on Monday after a tanker truck fire caused an overpass to collapse on Interstate 95.

The major highway is closed in both directions in Philadelphia after the tanker trunk carrying gasoline caught fire for reasons that were not yet clear. No deaths or injuries had been reported.

Officials said it would take several months to rebuild the stretch of the main north-south interstate on the East Coast, running from Miami to the Canadian border in the state of Maine.

"We're all going to need some extra patience in the coming days," Leslie Richards, chief executive officer of the Southeastern Pennsylvania Transportation Authority, which operates public transport, said at a Sunday press conference.

Pennsylvania Governor Josh Shapiro urged residents to look for alternative routes, to take commuter trains or to work from home if possible. The governor said he would make a disaster declaration on Monday, freeing up federal funds to help in the rebuild of a stretch of highway along which 160,000 vehicles pass daily.

The U.S. National Transportation Safety Board (NTSB) said the tanker was carrying gasoline and that it had sent a team to investigate.

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 degrees Fahrenheit, and that such incidents were not common.

Herrmann said Sunday's collapse might spark 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.

(Reporting by Jarrett Renshaw in Philadelphia, Brad Brooks in Lubbock, Texas, and Andrea Shalal in Washington; Editing by Donna Bryson and Raju Gopalakrishnan)