An ammonia leak at the JBS plant in Butchertown yesterday caused the evacuation of about 700 workers. Firefighters urged residents in the neighborhood to stay indoors in the hours immediately after the leak.About 80 pounds of anhydrous ammonia escaped from the plant at about 11:20 a.m Wednesday. High levels of ammonia can cause respiratory problems. Some Butchertown residents reported smelling ammonia after the leak. Louisville Fire and Rescue spokesperson Capt. Sal Melendez told the Courier-Journal that people might smell strong odors of the gas even if there are only trace amounts. Melendez said there were no levels of “harmful exposure” recorded outside the plant.Sirens sounded a little more than an hour after the event, advising people nearby to stay indoors. Residents got the all clear at about 2:15pm. Some residents complained the fire department waited too long to sound the sirens. Spokesperson Melendez says officials activated the sirens after increasing the threat level of the leak.