Rochester, MN (KROC AM News) - The Rochester Fire Department says the release of ammonia that shut down a section of North Broadway Tuesday night was caused by a over-pressurized relief valve.

A statement released by Deputy Fire Chief Steve Belau indicates the problem caused liquid ammonia to flow into a pipe that should only handle vapors, and that resulted in the release of ammonia vapor through a roof vent at the Kemps Ice Cream plant in the 400 block of North Broadway.

Belau says a passerby called 911 around 7 p.m. and reported a strong smell of ammonia in the area, which brought the Fire Department Hazmat team to the scene. The release of the toxic vapor prompted the closure of Broadway and the evacuation of the Kemps facility and some nearby businesses as a precaution, including the neighboring Taco Bell restaurant.

Belau says two Kemps workers were treated at the scene for respiratory irritation caused by exposure to the ammonia vapors, but did not require hospitalization.

The Fire Department cleared the scene around 9:45 p.m.

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