Authorities on Friday released the cause of death for the six workers killed in a nitrogen leak at a Gainesville poultry processing plant.

They died of asphyxiation caused by exposure to the frigid chemical at Foundation Foods Inc. on Jan. 28, according to the Hall County Sheriff’s Office. The autopsies were conducted by the GBI. No further information was released.

The plant uses nitrogen to flash-freeze. An issue with one of the freezer’s led to the leak, which is under investigation by various federal and state agencies. Nitrogen can cause the oxygen in the air around it to decrease.

About a dozen people were injured and taken to a hospital, and 130 people were evacuated.

Killed in the incident were Jose DeJesus Elias-Cabrera, 45, of Gainesville; Corey Alan Murphy, 35, of Clermont; Nelly Perez-Rafael, 28, of Gainesville; Saulo Suarez-Bernal, 41, of Dawsonville; Victor Vellez, 38, of Gainesville; and Edgar Vera-Garcia, 28, of Gainesville.