Fire broke out around 5 a.m. Tuesday at the Lilydale plant in northeast Edmonton. (CBC)Fire investigators were at the Lilydale Foods plant in northeast Edmonton Tuesday morning following an early morning fire in a shed on the site.

Fire crews were called to the plant at 127th Avenue and 77th Street around 5 a.m.

When they arrived, flames and smoke were coming from a shed that houses the plant's refrigeration units. The fire was under control in under an hour, but fire crews then had to deal with an ammonia leak, which continued throughout the morning.

Two people, including a firefighter, were sent to hospital to be treated for exposure to ammonia. A third person was treated at the scene.

A cause can't be determined until the ammonia leak is fixed, fire investigator Capt. John Yaschuk said late morning. "This fire is still under investigation," he said. "It did originate in a compressor room and it was pretty confined to that room."

While the fire didn't spread to the plant, production was temporarily shut down Tuesday.

"We believe the damage to be relatively minor," company spokesperson Connie Smart said. "Production may be impacted, but we're still in the process of assessing the situation at this point."

About 350 people work at the Lilydale plant, with half in the production plant and the rest in an on-site office building. The company processes and packages turkey and chicken products.

An air monitoring unit operated by Edmonton Fire Rescue determined that the air quality was safe.