A two-lane bridge collapsed in Pittsburgh, leaving a bus full of passengers dangling over the edge.

Rescuers had to drop nearly 150ft on ropes, while others formed a human chain to reach them.

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, authorities said.

Police reported the span, on Forbes Avenue over Fern Hollow Creek in Frick Park, came down at around 6am.

A photo from the scene showed a commuter bus upright on a section of the collapsed bridge.

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

Pittsburgh Bureau of Fire Chief Darryl Jones said three or four vehicles were involved in the collapse and there were 10 minor injuries with three taken to hospital. None of the injuries was life-threatening, Mr Jones said.

Authorities told motorists to avoid the area.

At the site of the collapse, Pennsylvania lieutenant governor John Fetterman said: “It’s just an awful, surreal scene.

“I hope it’s a wake-up call to the nation that we need to make these infrastructure investments.”

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

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”.

Authorities said on Friday that the bridge was last inspected in September but those reports were not readily available.

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.”