CHICAGO (CBS) — Two firefighters were among seven people taken to the hospital after an ammonia leak late Monday at Fresh Express in northwest suburban Streamwood.

Firefighters responded at 11:34 p.m. to an activated fire alarm at the industrial complex at 1109 E. Lake St., according to the Streamwood Fire Department. Workers reported a large ammonia leak from the refrigeration system at Fresh Express, which processes foods including packaged salads and vegetables.

The building was in full operation at the time of the leak and, although all employees were evacuated before firefighters arrived, several complained of breathing difficulty, fire officials said. Five workers were taken to St. Alexius Medical Center in Hoffman Estates.

Two firefighters that were exposed to vapors were also taken to the hospital for treatment, fire officials said.

As of Tuesday morning, HazMat technicians wearing fully-encapsulated suits have entered the building to measure ammonia levels and assess damage, fire officials said. The technicians expect to be at the building throughout the morning, ventilating the building to lower chemical concentration to safe levels.

The Streamwood Fire Department was assisted at the scene by personnel from Hoffman Estates, Schaumburg, Elk Grove Village, Elk Grove Township, Palatine, Mount Prospect, Arlington Heights, and Rolling Meadows.

(Source: Sun-Times Media Wire © Chicago Sun-Times 2017. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)