"Please avoid the area of Forbes and Braddock for a confirmed bridge collapse. Fire, EMS, and Police responding. No reported injuries at this time," Pittsburgh Public Safety tweeted.
It added that there is a strong smell of natural gas in the area and urged people to avoid the area.
"Gas line has been cut. Updates on injuries will be provided once PIO [Public Information Officers] is on scene," it said.
The Red Cross has been contacted for victim assistance.
A photo of the damaged bridge emerged online.
Meanwhile, Biden has been informed about the accident. The White House team is in touch with state and local officials on the ground, spokeswoman Jen Psaki tweeted.
The Pittsburgh police told the local WTAE-TV channel that no serious injuries have been reported.