A chemical leak at a West Virginia silver recovery business killed two people and sent 19 others to the hospital Wednesday, authorities said.

The incident occurred at the Catalyst Refiners plant in Institute as workers were preparing to shut down at least part of the facility, according to Kanawha County Commission Emergency Management Director C.W. Sigman. The leak involved a chemical gas reaction between nitric acid and another substance that resulted in what Sigman described as a "violent reaction" that "instantaneously overreacted."

Among those injured were seven ambulance workers who responded to the emergency. Other victims were transported to hospitals in private vehicles, including at least one case involving a garbage truck. All deaths and injuries occurred on the plant site, officials said.

The leak prompted authorities to issue a shelter-in-place order for the surrounding area, which remained in effect for more than five hours. The incident required a large-scale decontamination operation where exposed individuals had to remove all clothing and undergo spray-down procedures.

Catalyst Refiners specializes in removing silver from chemical process residues and is owned by Ames Goldsmith Corp. The company released a statement expressing sadness over the deaths and pledging cooperation with local, state and federal investigators. The facility is located near Institute, a community about 10 miles west of Charleston, the state capital.