A Port Authority bus that was on a bridge Friday when it collapsed is visible in Pittsburgh's East End. A two-lane bridge collapsed in Pittsburgh early Friday, prompting rescuers to rappel nearly 150 feet while others formed a human chain to help rescue multiple people from a dangling bus. Credit: Gene J. Puskar / AP

PITTSBURGH — The bridge that carries Forbes Avenue through Frick Park collapsed in Pittsburgh early Friday morning.

Pittsburgh Mayor Ed Gainey said three people were injured but no one was killed.

A photo from Post-Gazette news partner KDKA-TV showed at least four vehicles that had fallen into the chasm left by the collapsed bridge, with another vehicle dangling precariously over the edge.

Port Authority confirmed that one of its 60-foot articulated buses was trapped on a slab of the remnants of the bridge that fell into the ravine. Agency spokesperson Adam Brandolph said the bus driver and two passengers were able to escape and no one was injured.

The city warned the public to avoid the area near the intersection of Forbes and Braddock avenues, which split the Point Breeze, Regent Square and Squirrel Hill neighborhoods.

The bridge is about a quarter-mile from the Reynolds Street entrance to Frick Park. It goes over a wooded ravine and a creek that are part of the park.

Numerous police, EMS and park vehicles were at the scene Friday morning.

The collapse caused a large gas leak, which emitted a sound like a jet engine. Gas crews from Peoples Natural Gas on the scene were able to shut off the gas, Allegheny County Executive Rich Fitzgerald said.

Public Safety tweeted earlier that there was “a strong smell of natural gas in the area.”

Pennsylvania Gov. Tom Wolf wrote on Twitter that his office is “monitoring the situation” and “prepared to provide support as needed.”

News of the collapse came as the city prepares for a visit from President Joe Biden, who is scheduled to speak Friday afternoon at Mill 19 in Hazelwood.

Biden is expected to speak on infrastructure during his remarks, particularly with a stress on the importance of the recently passed $1 trillion bill that is intended to fund repair and maintenance of the nation’s roads, bridges, railways and other physical infrastructure.

Fitzgerald said Biden called him earlier Friday morning.

Pittsburgh Post-Gazette staff writers Ed Blazina and Julian Routh contributed to this report.