NEW YORK (AP) -- The bodies of all eight people reported missing after a deadly gas explosion destroyed two buildings have been recovered, the city fire commissioner said Friday, but workers are treating the scene as a rescue operation in case there are unknown survivors in the rubble.
Salvatore Cassano said no one else is known to be unaccounted for but workers will continue to scour the debris from the flattened apartment buildings for victims. More than 60 people were injured by Wednesday morning's explosion, and more than 100 others were displaced.
Cassano said about 70 percent of the debris had been cleared at the upper Manhattan blast site. But he said the pace was expected to quicken after firefighters removed a hazardous rear wall.
He predicted detectives and fire marshals would gain access to the East Harlem buildings' basements by midday Saturday to begin the investigation into what caused the explosion.
"Right now we are in the process of removing the final amount of debris," Cassano said. "We should be moving much more quickly now."
The rescue effort continued as federal investigators announced that gas was detected in underground tests of the site in the hours after the explosion, lending support to the hypothesis a gas leak may have been the cause.
National Transportation Safety Board team member Robert Sumwalt said utility Consolidated Edison dug dozens of holes up to 24 inches (60 centimeters) deep around the blast site and measured gas levels in them soon after the explosion. Gas concentration was up to 20 percent in at least five spots, and normal levels in the city's soil should be zero, he said.
"Somehow or another, natural gas did work its way into the ground," he said, adding that pressure testing of nearby pipes was beginning to look for potential leaks.
The NTSB, which investigates pipeline accidents, will conduct an inquiry after police and fire officials locate what might have sparked the blast.
Police have identified six of the dead: Griselde Camacho, 45, a Hunter College security officer; Carmen Tanco, 67, a dental hygienist who took part in church-sponsored medical missions to Africa and the Caribbean; Andreas Panagopoulos, 43, a musician; Rosaura Hernandez, 22, a restaurant cook from Mexico; George Ameado, 44, a handyman who lived in one of the buildings that collapsed; and Alexis Salas, 22, a restaurant worker.
Mexican officials said another Mexican woman, Rosaura Barrios Vazquez, 43, was among those killed.
The eighth body, of a woman whose name hasn't been released, was pulled from the rubble on Thursday.
Mayor Bill de Blasio, who toured a Red Cross shelter where residents of the destroyed buildings are staying, said Friday that the city would find temporary or long-term housing for about 50 displaced families.
"It's our obligation as the city of New York, and I know all New Yorkers feel this way, to stand by them," he said.
Investigators were trying to determine whether the gas leak had anything to do with the city's aging gas and water mains, some of which were installed in the 1800s. Cassano, the fire commissioner, said they'll look at meters, see if there were any breaks in the piping and identify any possible ignition sources, such as light switches.
On Thursday, Sumwalt, the NTSB team member, said the gas main and distribution pipe under the street had been examined in a crater and were found to be intact, with no obvious punctures or ruptures. They had not been torn from the ground.
However, he said, NTSB investigators had been unable to conduct a fuller examination because of the rescue effort, and it was unclear whether the leak came from inside or outside the buildings.
Fire and utility officials said that if the buildings were plagued in recent days or weeks by strong gas odors, as some tenants contended, they have no evidence anyone reported it before Wednesday.
The blast erupted about 15 minutes after someone from a neighboring building reported smelling gas, authorities said. Con Edison said it immediately sent workers to check out the report, but they got there too late.
Associated Press writers Jake Pearson, Ken Sweet, Julie Walker, Jonathan Lemire, David B. Caruso, David Crary, Leanne Italie, Karen Matthews, Deepti Hajela, Jim Fitzgerald, Mike Casey and Sonia Moghe contributed to this report.