A two-lane bridge has collapsed in Pittsburgh, prompting rescuers to rappel nearly 150ft while others formed a human chain to help rescue occupants of a dangling bus.

The collapse came hours before President Joe Biden was to visit the city to press for his trillion-dollar infrastructure bill, which includes bridge maintenance.

There were minor injuries from the collapse but no fatalities, said authorities, who also said they were flying drones to make sure no one was under any collapsed sections.

Bridge Collapse Pittsburgh
(Gene J Puskar/AP)

Police reported the span, on Forbes Avenue over Fern Hollow Creek in Frick Park, came down just before 7am.

Sam Wasserman, a spokesperson for Pittsburgh mayor Ed Gainey, said a few hours after the collapse that officials were evaluating the scene and an urban search-and-rescue team was still combing the area for any other possible victims.

He said most of the 10 people who were evaluated for injuries were first responders checked for exhaustion or because of the cold and snowy weather.

Three people were taken to hospital and none had critical injuries, Mr Wasserman said.

He said the articulated Port Authority bus was on the bridge when it collapsed, with a driver and at least one passenger who were evaluated by emergency medical responders.

Bridge Collapse Pittsburgh
(Gene J Puskar/AP)

City officials said the collapse caused a gas leak but the supply has since been shut off.

At the site of the collapse, lieutenant governor John Fetterman called it “just an awful, surreal scene”, adding: “I hope it’s a wake-up call to the nation that we need to make these infrastructure investments.”

Associated Press photographer Gene Puskar said the scene was reminiscent of the aftermath of an earthquake. There was a large crack on the end of the bridge where the bus was, he said, and there was also a car upside down in front of the bus.

Authorities told motorists to avoid the area.

Bridge Collapse Pittsburgh
(Gene J Puskar/AP)

In a statement, the White House said Mr Biden would proceed with his planned trip to Pittsburgh.

“Our team is in touch with state and local officials on the ground as they continue to gather information about the cause of the collapse,” the statement said.

“The president is grateful to the first responders who rushed to assist the drivers who were on the bridge at the time.”

The steel span, built in 1970, carries about 14,500 vehicles a day, according to a 2005 estimate.

Bridge Collapse Pittsburgh
(Gene J Puskar/AP)

Mr Wasserman said the most recent inspection was in September but the report was not immediately available.

A September 2019 inspection of the city-owned bridge revealed the deck and superstructure to be in poor condition, according to the US Department of Transportation’s National Bridge Inventory.

A spreadsheet on the state Department of Transportation website listed the bridge’s overall condition as poor, which, according to the Pennsylvania Department of Transportation, means “deterioration of primary structural elements has advanced”.