TUCSON, Ariz. -- Four workers have been treated and released at Tucson hospitals after being covered by cement dust at a plant.
Northwest Fire Department officials say two workers with the Staker Parson Cement Plant were covered with the dust when the hopper malfunctioned Monday.
Two other workers were covered by the dust when they went in to fix the broken valve.
Fire officials say dry cement dust was dispensed from the hopper and quickly became airborne.
They say the dust contains crushed and powdered limestone, which is a part of the mixture used in the production of cement.
Authorities say the limestone can cause breathing irritation and caustic burns, but isn't considered toxic.