Fire Commissioner Salvatore Cassano said rescue workers reached the rear of the basement Saturday. The next step is investigating the piping and meters in the front of the basement in an effort to determine what caused the blast that killed eight people.
Cassano 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 conducted 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.
An uplifting moment from the painstaking recovery effort came 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.
The church's pastor, Thomas Perez, suffered heart palpitations when he saw the Bible, said Letitia James, the city's public advocate. He was taken by ambulance to a hospital as a precaution, supporters said.
Cassano said Perez was overwhelmed with emotion.
"It was singed but it meant an awful lot to the pastor," he said. "It showed the pastor that they'll be rebuilding."
Truckloads of scattered material will be sifted for any traces of human remains that might not have been found at the site, Cassano said. Although the bodies of all eight people reported missing after Wednesday's blast have been recovered, the rescue operation was continuing in case others may be buried beneath the rubble, he said.
Meanwhile, newly released surveillance video shows groceries flying off the shelves inside the Park Avenue Mini Market, one block away, the moment the two five-story apartment buildings exploded and collapsed at 116th and Park.
A customer narrowly missed possibly being knocked off his feet.
Another camera on Park Avenue shows debris falling off the building after the explosion.
And across the street at the Armonie Restaurant the blast shook cameras and shattered windows, sending a dust cloud through the building.
Other surveillance video takes you in even closer, moments after the explosion.
It's loud, chaotic, and hard to see and breath, yet Sammy Carrastuillo, the man who recorded the video, ran to help a paralyzed woman who was trapped inside an ambulette.
"I was just thinking about 9/11 and wasn't trying to have another life lost so I just did what I had to do," Carrastuillo said.
The NTSB says gas concentration was up to 20% in five different spots after the explosion.
"That further leads to the possibility that this may have been a natural gas leak," an NTSB official said.
Mayor Bill de Blasio toured a Red Cross shelter where displaced families are staying.
The city has set up temporary housing, making dozens of apartments in East Harlem available.
"We will not let them fall; they've been through the unspeakable," Mayor de Blasio said.
Seven of the dead have been identified, while the eighth victim's ID has not been released.
The NTSB continues to investigate the cause of the explosion and is asking anyone with information or who may have witnessed or smelled anything in the days leading up to the blast to contact them at email@example.com.
On Friday afternoon, the Japanese Consulate confirmed that a Japanese national who lived in one of the destroyed buildings was reported missing. The consulate has not received confirmation that the eighth body recovered is the missing person from Japan.
"We are sure that one Japanese citizen is missing. That person was a resident of the building. Our office is in contact with police to find out as soon as possible what happened to this missing person," said a spokesman from the consulate. "We are anxiously awaiting for the identification of the eighth person recovered."
The deafening blast Wednesday morning destroyed two five-story apartment buildings at Park Avenue and 116th Street that were served by an 1887 cast-iron gas main.
The Associated Press contributed to this report.