GRANDVIEW, Mo. -- Federal investigators are on the scene of a massive explosion that destroyed a business Tuesday night.
The Bureau of Alcohol, Tobacco, Firearms and Explosives wants to know what caused the blast.
The city says 46 people had to be evacuated from the area around the Cedarwoods Apartments.
The explosion damaged 19 apartments in the complex, and rubble from the blast also rained down on nine homes further away, in what the ATF is describing as a 'significantly large debris field.'
"Our debris field is considerable for a building this size," said ATF Agent John Ham. "There was a significant event. We just have to figure out what caused it."
Firefighters reported at least a dozen more explosions after they arrived at JW's Lawn and Garden Equipment, including multiple pops of what some believe to be ammunition going off.
Wednesday morning ATF experts scoured the blast zone, looking for evidence to help determine the cause.
Investigators say natural gas has been ruled out, but they continue to investigate reports of gunpowder used for ammunition reloading, fireworks, or even dynamite that may have been at the business.
Those who were forced to leave their homes say whatever the cause, it had to be something big.
"Honestly i thought it was an attack or something," said Willie Cross, after escaping significant damage to his apartment. "It was like being in a war zone. It’s like you hear a big 'Ba-Boom!' Then it was like 'Boom!' Then it sounded like hand grenades. Then it sounded like automatic fire. 'Bop, bop, bop, bop, bop, bop, bop, bop, bop!' It was crazy. It was wild."
The ATF says fire continues to burn Wednesday morning in the basement of the structure, preventing explosive experts from getting a closer look.
The ATF says reloading ammunition is legal under both federal and state law, but investigators also say the amount of gunpowder required to cause such a big blast would be considerable.
Those displaced by the blast are returning home but say it may be difficult to keep warm overnight with boarded-up windows. Temperatures are too cold for the windows to be fully replaced before the evening arrives.
The city says the business owner is talking to investigators. The ATF also reports a dog that was kept at the business is missing.