BUENA, New Jersey (WPVI) -- Authorities in Atlantic County said Tuesday that they have determined the cause of a house fire and explosion that killed four people earlier this month.
Investigators said the August 3 fire was sparked by an enormous amount of explosives found on the first floor of the home in Buena.
"A large amount of explosive materials and precursors were seized from a vehicle on scene, as well as an outbuilding on the property," said Franklin Township Police Chief Matthew DeCesari.
Due to the damage at the home on N. West Boulevard, the Atlantic City Police Department Bomb Squad couldn't determine the exact explosives that caused the blast.
However, police said all of the items recovered are consistent with the production of commercial-grade fireworks.
Some of the items recovered include 99 pounds of potassium nitrate, 58 pounds of ammonium nitrate, and 10 pounds of barium nitrate. According to the National Library of Medicine, these three chemicals can be used to make explosives.
Chief DeCesari said most of the materials alone are legal to possess.
"However, if you start to mix them, they become materials that could potentially be explosive, and at that point, they become illegal to possess," he explained.
On the property, police said they also found aerial shells and homemade pyrotechnics.
In July, authorities said they found evidence of the possession of fireworks in the neighborhood, but no criminal charges were filed.
A 1-year-old girl and a 16-year-old girl were among those injured in the explosion.
Both victims were flown to St. Christopher's Hospital for Children in Philadelphia.
Police say the 1-year-old is in critical, but stable condition after suffering from burns. They say the 16-year-old is set to be released from the hospital soon.
Authorities say a 2-year-old boy, a 3-year-old girl, and two men ages 52 and 73 died in the explosion.
Their identities have not been released.
Video from Chopper 6 immediately after the explosion showed the home had been reduced to rubble and debris could also be seen around the yard.
Neighbors said the explosion was so large that car alarms in the area started going off.
Gas utilities have been ruled out as being an attributing factor, investigators said.
Federal and local partners assisted with the investigation.