A recent accident at the Anniston Army Depot sent four depot workers to the hospital after they were exposed to nitric acid.
The accident, which occurred July 30 at the plating shop of the depot's Nichols Industrial Compex, is under investigation.
Further details are being withheld while the depot's Safety Office conducts its investigation.
"There's an investigation going on right now, so until the investigation is over, we can't comment on it," said Joan Gustafson, public affairs officer at the depot.
Nitric acid is used in the day-to-day activities at the depot as workers put armored plates on vehicles.
It is a colorless, highly corrosive and poisonous liquid that emits fumes that can choke in certain types of air, according to the Columbia Electronic Encyclopedia.
Nitric acid is also a strong oxidizing agent and reacts with metals, oxides and hydroxides.
Depot officials did not release any of the injured workers' names.
"Three workers are back at work," said Ray Van Schoubroek, who works for the depot's union office.
One worker still is hospitalized, Van Schoubroek said, but he didn't comment further.
Ms. Gustafson said results of the investigation could be released sometime next week.
