MEQUON, Wis. (CBS 58) – Investigators are working to figure out what caused a fire to sweep through a Mequon business Monday night.

When crews arrived at Charter Manufacturing, they found the roof completely engulfed in flames. Crews worked throughout the night to put the fire out and extinguish hot spots. Mequon’s fire chief says it was a tough fire to battle because of fire hiding behind short walls in the roof.

“It's a one and a half story building, there's a knee wall in there and it's kind of concealing the fire behind some void spaces that we keep trying to find,” says Mequon Fire Chief David Bialk.

No one was hurt in the fire and there's no word yet on how much damage the fire caused.