NEW YORK, JULY 21 -- Propane gas spewing from a damaged tank touched off an explosion and fire today that leveled three two-story buildings in a Brooklyn neighborhood, killing four people and injuring 35, officials and witnesses said.

Two victims were seriously injured, and 12 firefighters and 12 police officers suffered minor injuries, officials said.

Scores of firefighters hunting for victims dug through the rubble in what Deputy Commissioner John Mulligan described as "a brick-by-brick, beam-by-beam search" of the buildings in the Borough Park section.

"We believe all persons have been accounted for," said Fire Commissioner Joseph Spinnato. "But there is a remote possibility there were others inside."

Police Capt. Michael Julian said an employe of a plumbing supply business told police that eight people were in the store 15 minutes before the blast. Police have accounted for six of those, he said.

A crane was brought in to lift the building's fallen roof.

An eyewitness, Ari Dubov, said two workers were unloading propane tanks from a truck into a plumbing supply store when the tanks "banged together, and one of the nozzles broke off." The flammable gas began hissing out, he said, and the workers ran to warn people in the store.

Moments later, at 9:47 a.m., "there was a phenomenal explosion," said Rabbi Elliot Amsel of Congregation Hamaor, across the street from the blast. "Now it looks like London in World War II."

The three two-story brick buildings, in a neighborhood of tree-lined streets, housed a plumbing business, a bakery and apartments.

"Everybody was there with bare hands, digging, pulling out rubble, pulling out survivors," said Volve Herman, 35, an ambulance attendant. He described pulling out three men -- two alive, one dead -- from under two feet of rubble on the sidewalk.

Dubov, a 28-year-old truck driver, said that as the workers carried the containers, "Somehow, they just, like, banged together, and one of the nozzles broke off."

Dubov, watching from across the street, said he heard a hissing noise and "saw the vapor coming out" from a container. The two men "ran in {to the store} to try to get out as many people as they could," he said. "By the time they came out, the whole building just came down" in "a tremendous explosion."

It was not known what ignited the propane, Spinnato said. The explosion broke a gas pipe and the escaping gas fed the fire, according to Homer Bishop, the Fire Department's chief of operations.

Two survivors were in the operating room of Maimonides Hospital, and nine others were treated for injuries, mostly smoke inhalation. Twelve police and 12 firefighters were treated, mostly for smoke inhalation.