Northwest Fire District paramedics responded to a McDonald's on Cortaro Road and I-10.
The Northwest Fire District Hazmat team was first involved, because of the amount of people who were sick in one location.
According to Northwest Fire's Adam Goldberg, a 19 year-old employee had complained of difficulty breathing, light-headiness and dizziness.
Paramedics found her semi-conscious and she was treated and transported to the hospital. She is in serious condition.
Other employee's complained of having the same symptoms.
According to the manager on duty, the kitchen area had been without air conditioning for a week.
They determined the temperature inside was 96 degrees.
McDonald's will be closed until tomorrow.
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