The fire at a vacant building in Ansonia last week is now being investigated as arson.

The fire erupted Friday at the old Ansonia Copper & Brass building on Liberty Street. No one was injured.

Firefighters said they saw heavy fire coming from the windows upon arrival. The building's roof caved in because of the blaze.

A reward of up to $2,500 is being offered for anyone to help identify who may have started the fire. Anyone with information is asked to call Ansonia police, Fire Marshall's Office or the CT Arson Hotline.