Officials investigated Friday what caused the brick façade of a 20-story residential building in Manhattan to bulge.

Among the tenants at 2 Fifth Avenue, near Washington Square Park, is former Mayor Ed Koch.

The affected parts of the building's wall were secured with large wooden beams.

Fire officials were afraid that bricks would fall on passersby, but the wall was soon secured.

"We have about a 25-feet section of wall, between the 17th and 18th floors, that apparently the tiebacks that hold the bricks into the main structure of the building have either corroded or come loose, and the bricks are bulging out of the wall," said FDNY Deputy Chief James Daly. "There are fire department units on scene that are building a temporary wall brace to keep the entire 25-feet section of brick into the building."

No one was evacuated

Department of Building officials were in the process late Friday of issuing violations to the building's owner.