An investigation has begun into what is believed to have been a chemical leak at East Midlands Airport.
Emergency crews were called to a part of the airport owned by the delivery company DHL at 1015 BST on Tuesday.
The air ambulance was also dispatched on what was considered a "possible life- threatening situation".
The area was evacuated while about 20 fire officers dealt with the leak which is thought to have been a result of gas escaping from a refrigeration unit.
A spokesperson for East Midlands Ambulance Service said people were treated at the scene by paramedics for minor injuries as a result of the gas seeping into the air conditioning system.
She added the call had been logged as category A - meaning the incident could have been immediately life-threatening.