Staffordshire Fire and Rescue Service were called to an incident at Brakes Chilled Food Distribution, Bonehill Road in Tamworth at 11.50am today.
Tamworth Area Commander, Del Roberts commented: "There has been a chemical leak which we can now confirm is a small amount of ammonia. Brakes Chilled Food Distribution has been evacuated however there is no cause for concern regarding the ammonia.
"We had six crews in total at the scene from Tamworth, Lichfield, Burton, Stone and Hanley and one crew from over the border was also in attendance.
"We are currently discussing how best to isolate the leak with an onsite specialist."