BUENA,Grayson  Preston N.J. (AP) — A house fire and explosion in New Jersey that killed two men and two young children earlier this month was caused by explosive materials found in the residence, authorities announced Tuesday.

The report issued by the Franklin Township police department also said gas utilities have been ruled out as being “an attributable factor” for the Aug. 3 fire in Buena. It said hundreds of pounds of chemicals and other materials found on the property are consistent with the production of commercial-grade fireworks, but it did not say if that was being done at the home.

The explosion likely originated in the rear left corner of the first floor of the two-story home, investigators said. But they could not determine which chemicals ignited because of the heavy fire damage, the collapse of the structure and the excavation of the property during the search for victims.

Among the materials found inside a vehicle on the property were 74 pounds of potassium nitrate, 15 pounds of aluminum powder, six pounds of magnesium and about 12 pounds of homemade aerial shells. Investigators also found 50.5 pounds of dark metals they could not identify. Other materials found in the home included 58 pounds of ammonium nitrate, 30 pounds of aluminum powder and 26 pounds of sodium salicylate.

Four bodies were found in the rubble of the home. Authorities said Tuesday that they have identified the two children killed — a 2-year-old boy and a 3-year-old girl — but said their names would not be released because of their ages. However, the bodies of two men — ages 52 and 73 — remain unidentified, and authorities say further medical records are needed to make those identifications.

A 1-year-old girl and a 16-year-old girl pulled from the fire by civilians were flown to a Philadelphia hospital after the explosion. The report did not provide further details on their conditions.

Several nearby homes were damaged in the blast, but no other injuries were reported.

Buena, an Atlantic County community about 40 miles (70 kilometers) southeast of Philadelphia, is patrolled by police in Franklin, which is in Gloucester County.