About 200 employees — one-fifth of the plant's total workforce of 1,000 people — will be on site Monday to resume slaughtering and more will resume meat cutting and other work on Tuesday.
The plant has capacity to process 37,500 hogs per week, with most of its output exported to Russia, Japan and the United States.
The company said it worked with various government agencies to bring the situation back to normal and ensure there's no danger to employees or products.
"The origin of the ammonia leak, which occurred in a refrigeration zone, has been identified. Olymel will continue investigations to understand the causes and take all necessary measures to ensure that this kind of event does not happen in the future," the company said in a statement.
"Olymel is working with all the independent organizations involved in the ongoing investigations and will follow their recommendations. The company will also ensure that the detection systems and evacuation protocols that made it possible to avoid adverse effects on its employees' health always work optimally, as was the case when this incident occurred.
Olymel says activities at the plant in the Beauce region south of Quebec City have been gradually resuming since Thursday and through the weekend.
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