An explosion rocked a working-class neighborhood and destroyed six row houses last night, killing two people and leaving a third missing, authorities said.

The blast knocked people to the ground, blew out the front of one house and collapsed three others around it. Two adjoining houses were destroyed by the explosion and the three-alarm fire that followed. Four other people were injured.

Firefighters had the blaze under control in half an hour, but smoke and steam continued to boil out of the rubble of the century-old houses. About a dozen other homes were evacuated.

Authorities removed the bodies of an elderly man and an elderly woman from the houses. Fire Commissioner William Richmond said one other person, a teen-aged girl, was missing.

"We are hand-picking through the rubble now, piece by piece, trying to see who might be down there," said Mayor W. Wilson Goode, who was at the scene with Richmond.

Robert Burns said he was watching television when the explosion hit. "We heard this big bang, came out and saw people dropping all over the street from the concussion. When we got to the rubble, there was a big smell of gas. I brought one lady out who had her whole head cut wide open."

The cause of the blast was not known, said Philadelphia Gas Works spokesman Avrom Steinbrook.