Six workers died on Wednesday at Prospect Valley Dairy near Keenesburg, about 35 miles northeast of Denver, after emergency crews responded to what authorities described as a “confined-space rescue.” Firefighters recovered the bodies from an underground area around 6 p.m., according to Southeast Weld Fire Protection District Chief Tom Beach. Three other people were treated at a nearby hospital and released. Weld County Deputy Chief Coroner Jolene Weiner said the deaths are being investigated as the possible result of exposure to toxic gas in a confined space; autopsies and toxicology tests are pending. The Occupational Safety and Health Administration has opened an inquiry that could take up to six months, while the Weld County Sheriff’s Office said it has found no indication of criminal activity. On Friday Weiner released the names of the victims, all Hispanic males: Alejandro Espinoza Cruz, 50; his sons Oscar Espinoza Leos, 17, and Carlos Espinoza Prado, 29; their relative Jorge Sanchez Pena, 36; Ricardo Gomez Galvan, 40; and Noe Montanez Casanas, 32. Oscar Espinoza was a Highland High School student, district officials confirmed. Prospect Valley Dairy is owned by Prospect Valley Dairy LLC and is a member of the Dairy Farmers of America cooperative, which called the event a “tragic accident.” Weld County, Colorado’s leading dairy-producing region, is also under review for workplace-safety practices in the wake of the fatalities.