Six workers at a chicken processing plant in Georgia were killed by a liquid nitrogen leak Jan. 28, according to local authorities.

The accident at Prime Pak Foods in Gainesville, a center of Georgia’s chicken processing industry, also hospitalized nine other workers, three in critical condition. Five workers died at the plant and one more in a hospital emergency room. Prime Pak was taken over this month by Foundation Food Group, a poultry company with headquarters in Gainesville.

Authorities said the leak’s cause was unknown. Liquid nitrogen is used for cryogenic freezing and, in some cases, as a component in mechanical refrigeration systems.

Prime Pak processes whole raw chickens into chicken fingers and other cuts for foodservice customers.