BRENTWOOD, N.Y. — Police say a propane explosion destroyed a suburban New York house that killed a toddler and injured 17 other people. But officials say they are still trying to determine what ignited the gas.

Suffolk County authorities returned to the scene Wednesday in the middle-class neighborhood of Brentwood on Long Island.

Police on Wednesday confirmed preliminary suspicions that propane was the cause. Two 200-pound propane gas tanks were on the premises, but no natural gas lines were present.

On Tuesday, the entire structure was reduced to small shards of wood, plywood, drywall, insulation and other materials.

The 18-month-old boy's parents were among four other residents who were injured. A plumber and insurance company representative visiting the home, seven police officers, two firefighters and two neighbors also were hurt.