The alleged pin hole leak happened in the refrigeration area of Kepak, Watergrasshill, last Sunday.
Forty employees were in the factory at the time of the leak but none were working in the immediate vicinity.
According to Kepak, six staff starting the morning shift yesterday detected what they described as a lingering trace of ammonia in the building.
As a safety precaution they were referred to a local GP for a check-up but did not need medical treatment.
The fire brigade attended the factory as a precaution. They checked the air quality and confirmed there was no health and safety issue.
The Environmental Protection Agency, the Health and Safety Authority, and the Department of Agriculture were informed of the incident.
Kepak is also carrying out its own internal investigation.
“Food product in the affected area was all packaged thus no unpacked meat was exposed to the leak,” the Kepak spokesman added.
The plant was evacuated for a short period while the leak was fixed.
“Routine safety procedures were immediately deployed. A small number of staff working in the plant at the time were evacuated while the leak was quickly rectified with no injury to staff,” the spokesman added.
The Watergrasshill factory is one of the largest Kepak plants in the country.