The Kaukauna fire department responded to a fire at a paper mill overnight. Fire crews were called around 3:30 a.m. Sunday to Expera Specialty Solutions on the 600 block of Thilmany Road. When crews arrived, the sprinkler fire system had knocked down most of the fire. Firefighters found fire and heavy smoke in the ventilation system and was able to extinguish the fire quickly. The fire started in the ventilation system, according to the Kaukauna Fire Department. The fire was extinguished by 4 a.m. There were no injuries. There is minimal damage to the building.