Investigators will work over the next few days to determine what caused the 11-alarm fire in Passaic.

Mayor Hector Lora says demolition of the destroyed building has already started. Fire officials will be on a fire watch into Monday morning – meaning they will be looking for potential flare ups or existing fires deep inside the rubble.

Lora thanked first responders for all their hard work in the last few days.

"Today, we see evidence of the remarkable and the tremendous efforts of the heroic firefighters that came from all over our area…[who prevented] the fire from reaching the main chemical plant,” he said.

He added that the air quality is still safe.