National Briefing

A large blaze gutted part of a meatpacking plant south of Milwaukee, and authorities warned thousands of nearby residents to evacuate because of the possibility of toxic fumes or an ammonia explosion. The warning was lifted about 7 p.m.

The fire at the Patrick Cudahy Inc. plant in Cudahy, a suburb of Milwaukee, started Sunday night.

Firefighters contained the ammonia, which is used in refrigeration, to part of the plant where flames were not expected to reach, Fire Chief Dan Mayer said, adding that he was “cautiously optimistic” an explosion would be avoided.

Ammonia also may be fatal if inhaled. Nearby residents were told to evacuate because of the threat of toxic fumes, but Mayor Ryan McCue said the order was lifted because no ammonia had been detected.

Five people sought treatment for breathing problems. Three were hospitalized, each with underlying health conditions that made them more vulnerable.