The incident was reported at approximately 9:31 am local time at Catalyst Refiners, a silver recovery facility located in the community of Institute, about 16 kilometers northwest of the state capital city Charleston, Xinhua reported.
Preliminary investigations indicate that the plant was in the process of shutting down operations, with workers engaged in cleaning and decontamination activities in preparation for closure, according to a press release by the Kanawha County Commission.
It is believed that a chemical reaction occurred during that process, triggered by the unintentional mixing of two chemical agents, producing hydrogen sulfide, a toxic, colorless gas with an odor of rotten eggs, said the Kanawha County Commission.
The reaction caused "a violent reaction of the chemicals and it instantaneously overreacted," CW Sigman, the county commission's emergency management director, said at a briefing.
Among those hospitalized were seven ambulance workers who were responding to the leak, officials said. In the chaotic aftermath, victims were transported to local hospitals in private cars and even a garbage truck, Sigman said.
Authorities did not immediately release further details on the identities of the victims or the conditions of those hospitalized.
Ames Goldsmith Corporation President Frank Barber issued a statement acknowledging that two employees had died. "Ames Goldsmith Corp is deeply saddened by the deaths of two of our colleagues," Barber said, adding that the company was cooperating fully with local, state and federal agencies to determine the cause of the incident.
West Virginia Governor Patrick Morrisey issued a statement confirming that the state's Emergency Management Division, Department of Health, and Department of Environmental Protection had all been activated and were coordinating with county authorities.
"Our top priority is the safety and well-being of our citizens," the governor said. "We are working around the clock with local officials to ensure this incident is contained and that all necessary state resources are on the ground to protect the community."