Firefighters, medics and hazmat crews responded to Mrs Resslers meat packing plant, along the 5500 block of Tabor Road.
Investigators say someone noticed ammonia leaking from a 30 gallon drum.
The leak formed a vapor cloud inside part of the building, injuring two workers.
Those workers were transported to Temple University Hospital, where they are reported in stable condition.
The incident remains under investigation by the city's Fire Marshalls Office and L and I inspectors.