PITTSBURGH (AP) — An apparent explosion showered bricks on a dense residential neighborhood and shattered windows blocks away Friday, leveling two row houses and damaging at least two dozen other homes. No injuries were reported.

The cause was not immediately known, but a blast appeared to have originated in one of the two collapsed houses, said Robert McCaughan, the city's chief of emergency medical services. The house was owned by the city and had been condemned, according to Allegheny County property records.

It was vacant, and the gas service had been turned off, company spokesman David Spigelmyer said.

The second collapsed home was owned by a man who had been living at a nursing home, said Ray Wappes, 47, the longtime owner of a rental house across the street that was damaged.