Just across the state line in Illinois, Rockton Fire Chief Kirk Wilson says it could take another week for a half-million gallons of oil at the Chemtools fire site to burn off.
84 fire departments are working in shifts at the scene four miles south of Beloit.
A one-mile radius around the plant remains evacuated until the heavy smoke from the fire is brought under control.
Local officials say about 1,000 people are affected by the evacuation order.
No injuries were reported among the 70 people who were working at the plant when the fire started.
Two firefighters suffered minor injuries.
