NEW YORK (AP) — Workers searching a pile of rubble from a gas explosion are using sound devices to probe for voices and telescopic cameras to peer into small spaces.

Fire Department of New York Chief Edward Kilduff says they're working "with hope" for the possibility of finding survivors.

The search is slow going. Forty percent to 50 percent of the debris was removed by Thursday evening. Kilduff says a fire is still burning, and the force of the explosion collapsed and pancaked layers of floors. A back wall is still freestanding and poses a collapse hazard.

Workers are planning a full day of work Friday removing debris. They're hoping to make it down to the first floor by Saturday and then move onto the basement.

At least eight people died in Wednesday's blast.