Digging through debris with heavy equipment will be vital to finding any survivors, recovering remains and learning what caused the deadly East Harlem gas explosion that destroyed two apartment buildings, officials said.
"We are still looking at this as a potential rescue operation," FDNY Chief of Department Edward Kilduff said Thursday evening.
Backhoes are clearing the hulking, 2-1/2-story debris pile at the Park Avenue scene, but Kilduff called it a "very deliberate operation because of safety concerns and the fire that is still burning."
Kilduff estimated that crews have removed nearly half of the debris so far.
The condition of the remaining structure is precarious, however. Of particular concern is a freestanding back wall that Kilduff said is a "significant hazard for us." Removal of the wall is being handled by a private contractor, he said.
Kilduff said it may take a couple of days before investigators can safely access the basement, which may hold clues to what triggered the Wednesday morning blast.
Telescoping video is being used to look for people who may be trapped in the rubble when a body is found, he said. NYPD search dogs were used early on without success.
Avoiding remaining hot spots, rescue and recovery crews are starting at the top of the pile, then moving to the rear and inside, said Salvatore Cassano, New York City fire commissioner. Those workers have been wearing masks to avoid breathing in hazardous fumes.
Heavy-duty evacuation equipment at the scene includes a machine known as "the grappler" that is used to move rubble.
"We are continuing rescue operations, hoping to find others still alive," Mayor Bill de Blasio said after surveying the scene early yesterday.
"These rescue operations will continue for an open-ended period of time," he said. "There will be disruption in the immediate area because we have to continue this rescue operation. We're very devoted to it."
Authorities have evacuated 89 residential units and three businesses in seven nearby buildings while rescuers work, the mayor said. City building inspectors have scrutinized those structures and concluded they are not in danger of collapse.
With Anthony M. DeStefano