Thirteen people were hospitalized for heat-related illnesses at a post office in Chicago Saturday morning.
Employees said the air conditioning at the post office was not working, and the temperature was at least 100 degrees inside.
About 10 ambulances were called to the scene.
Authorities said people were suffering from heat exhaustion, heat stress, and dehydration.
The building was evacuated and several dozen postal workers were seen getting into a cooling bus parked outside.
A spokesperson for the postal service said employees were relocated to another post office nearby.