Hundreds of staff have been evacuated from the Maple Leaf Foods' plant on Courtland Avenue in Kitchener after an ammonia leak was discovered in the facility.

Workers were moved off-site to the corner of Courtland Avenue and Stirling Avenue on Tuesday afternoon after the leak was discovered.

The ammonia leak was in the office tower and spread throughout the building, said Maple Leaf senior supervisor Rick Vogel.

Vogel added an estimated 700 to 800 employees were in the Maple Leaf facility at the time of the leak.

Two people were assessed at the scene by EMS workers and a third was taken to hospital.

Maple leaf plant ammonia leak

Workers were forced to evacuate a Maple Leaf Foods Plant in Kitchener after an ammonia leak was discovered. (Amanda Grant/CBC)

Six fire crews and a hazardous materials team were at the site testing the air quality.

"The air monitoring that we've done is at safe and acceptable levels," said Kitchener Fire Chief Tim Beckett. "We've got a good wind going and the ammonia is dissipating."

Beckett said there were two leaks at the facility.

While he advised nearby residents to stay inside and close windows and doors, he said an evacuation of those homes was not warranted. 

Courtland Avenue has been closed between Borden Avenue and Palmer Avenue as crews continue to work.