Police are investigating whether something other than gas caused a building to explode in Brooklyn over the weekend.
An NYPD spokesman says the gas was shut off on the floor where investigators think the blast started.
Authorities initially believed the blast occurred because a stove was removed from a gas line they thought was not properly disconnected.
Crews on Wednesday ripped apart what was left of the two buildings on 13th Avenue while Fire marshals were back at the scene examining floor boards and other debris.
Police say those investigators were looking for traces of chemicals that might have contributed to the explosion and fire.
A body was pulled from the wreckage Monday, but authorities have not confirmed whether the body is that of 47-year-old Francisca Figueroa.
Relatives say she lives on the second floor of the building on 13th Avenue near 42nd Street in Borough Park.
She has been missing since Saturday afternoon's blast.
Another woman, 64-year old Ligia Puello, was killed in the explosion.
About 50 people are still displaced.
Some have received hotel vouchers from the Red Cross.
Meanwhile, about a dozen businesses between 42nd and 41st streets remain closed during the demolition.
Some owners and employees are being allowed back to survey the damage.
Many businesses on surrounding blocks opened Wednesday for the first time since the explosion because of Jewish holidays on Monday and Tuesday.