Members of the Friendly Hands Ministry church take part in a Vigil next to a site of an explosion in East Harlem on March 13, 2014 in New York City. Kena Betancur/Getty Images
Emergency workers sifted through debris Saturday from the site of a deadly explosion at two New York City apartment buildings as they worked to clear the way for investigators to search for clues that might reveal what caused the blast.
Fire Commissioner Salvatore Cassano said rescue workers reached the rear of the basement Saturday, but added that investigation of the piping and meters in the front of the basement, which it is hoped will help explain what caused the blast that killed eight people, will likely start on Sunday.
He said that the National Transportation Safety Board should be able to start pressure-testing the pipes Sunday.
Arson detectives and fire marshals have been waiting to enter the basements to examine meters, check pipes and inspect any possible ignition sources, such as light switches, that might have caused the blast.
The theory that the explosion was due to a gas leak gained momentum Friday after the NTSB, which investigates pipeline accidents, said underground tests done in the hours after the explosion registered high concentrations of natural gas. The NTSB will conduct its own inquiry after police and fire officials determine what might have caused the blast.
The painstaking recovery effort provided a small, uplifting moment as crews pulled a large, water-damaged Bible from the rubble of the Spanish Christian Church, which was located in one of the two destroyed buildings. About two dozen people, including clergy members, carried the Bible in a solemn procession near the East Harlem site.
"This was in the depths of the rubble. Somehow God protected it," said Rick del Rio, a bishop at the Church of God.
Although the bodies of all eight people reported missing after Wednesday's building collapse have been recovered, the rescue operation was continuing in case others may be buried beneath the rubble, Cassano said.
More than 60 people were injured in the explosion, and more than 100 others were displaced.
Police have identified six of those who died: Griselde Camacho, 45, a Hunter College security officer; Carmen Tanco, 67, a dental hygienist who participated 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 name of the eighth person recovered, a woman, hasn't been released.
Investigators were trying to determine whether the explosion had anything to do with the city's aging gas and water mains, some of which were installed in the 1800s. More than 30,000 miles of decades-old, decaying cast-iron pipe are still being used to deliver gas nationwide, according to U.S. Transportation Department estimates.
Fire and utility officials said that if the buildings were plagued in recent days or weeks by strong gas odors, as some tenants contend, 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.
Reports of strong gas odors by area residents are bolstered by two reports that examined the city's aging gas pipelines.
A study released the same week as the blast found that nearly two-thirds of the city's 6,300 miles of gas pipeline is made of material that is vulnerable to leaks.
The report, commissioned by the nonprofit Center for an Urban Future, looked at New York City's aging infrastructure including its gas pipelines. It found that 58 percent of ConEd's 2,234 miles of gas mains pre-date 1960. Sixty percent are composed of unprotected steel or cast iron, the most leak-prone material.
In 2011, the federal government created a program aimed at moving municipalities away from "high-risk pipeline infrastructure" constructed of cast, wrought iron, or bare steel.
The initiative, administered by the Department of Transportation, emphasized the importance of "eliminating aging infrastructure in each state" and encouraged states to make information about pipelines and the safety record of pipeline operators easily accessible to the public.
The agency found that 11 percent of the incidents occurring on gas distribution mains involved cast iron mains.
The main pipeline into the building that exploded "was partly made of cast iron and dated back to 1887," ConEd confirmed to Huffington Post.
A separate report from 2013 concluded that Manhattan sits in a cloud of elevated levels of methane. The survey, commissioned by environmental group Damascus Citizens for Sustainability, highlighted the lurking danger posed by leaks of natural gas, a mixture that is mostly methane.
Researchers conducted a series of tests around Manhattan to identify natural gas leaks. "The methane measurements in Manhattan indicated many leaks, some intense. Very few measurements indicated normal background methane levels," the survey said.
Methane is a potent greenhouse gas that is responsible for nearly as much global warming as all other non-CO2 greenhouse gases put together.
The report, which examined the leaks in the context of global climate concerns, noted the "public health threat of constantly escaping natural gas evidenced by elevated methane levels."
Meanwhile, Mayor Bill de Blasio pledged his support to find suitable temporary or long-term housing options for those displaced by the blast.
His promise followed a tour of a Red Cross shelter Friday where some of the displaced residents have been housed temporarily.
"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.
Al Jazeera and The Associated Press. Amel Ahmed contributed to this report.