Firefighters poured millions of gallons of water on a pesky fire that's gutted part of a sprawling meat packing plant in the suburb of Cudahy just south of Milwaukee.

Officers told thousands of people living within a mile of the Patrick Cudahy plant to leave because of the smoke and threat of toxic fumes.

The fire started Saturday night and continued all day. Sometimes it seemed to die down and then flared up again. Cudahy Mayor Ryan McCue says urged people to conserve every drop of water they could because more than eight million gallons had already been poured on the fire.

Four people went to Aurora St. Luke's South Shore hospital with breathing problems. The hospital says one was treated and released. Three elderly people were admitted, and all of them had underlying health conditions that made them more vulnerable.

Smithfield Foods owns the Patrick Cudahy plant and is evaluating what effect the damage might have on customers.

But a plant spokesman says less than half the plant was affected, and operations could resume in unaffected areas by the end of the week.