Cause of Death Revealed for Six Workers at Colorado Dairy Farm

Authorities have revealed the possible cause of death for six people, including a father and his two sons, who tragically died while working at a Colorado dairy farm in August 2025. The Weld County coroner’s office determined the victims were exposed to hydrogen sulfide gas at Prospect Valley Dairy in Keenesburg.

The Associated Press reported on Oct. 30 that toxicology tests and autopsies confirmed the gas exposure as the likely cause. The August 20 incident has since prompted an ongoing investigation by the Occupational Safety and Health Administration (OSHA).

Hydrogen Sulfide Exposure Cited in Dairy Farm Tragedy

The six victims have been identified as Alejandro Espinoza Cruz and his sons, 17-year-old Oscar Espinoza Leos and 29-year-old Carlos Espinoza Prado. Also among the deceased were a relative by marriage, 36-year-old Jorge Sanchez Pena, and two other men: 40-year-old Ricardo Gomez Galvan and 32-year-old Noe Montañez Casañas.

Officials said the group was working in a confined area at Prospect Valley Dairy when they were fatally exposed to hydrogen sulfide, a toxic gas often referred to as “sewer gas.” It is colorless and emits a rotten egg odor that can quickly become undetectable due to “olfactory fatigue.”

The coroner’s office described the deaths as “an industrial accident in a confined space at a dairy farm.” Emergency crews were dispatched to the site around 6:00 p.m. that evening. Fire Chief Tom Beach of the Southeast Weld Fire Protection District said that responders entered the confined space with caution but found all six workers deceased.

Ongoing Investigation and Workplace Safety Concerns

Hydrogen sulfide forms naturally in manure pits, sewers, and other enclosed areas where organic matter decomposes. According to OSHA, exposure to high concentrations can cause rapid unconsciousness and death within minutes.

The incident has sparked renewed discussion about agricultural workplace safety, particularly for dairy and livestock operations that rely on confined-space systems. The ongoing OSHA investigation is expected to examine whether proper ventilation, gas monitoring, and safety training were in place at the time of the accident.

Prospect Valley Dairy, owned by Prospect Ranch, has not issued a public statement. The coroner’s findings have provided the first major update since the tragedy, bringing some clarity to families awaiting answers for over two months.

The cause of death — hydrogen sulfide poisoning — underscores the dangers agricultural workers face when operating in enclosed environments without sufficient protection. Officials say the investigation into the farm and its contractors may take up to six months to conclude.

FYI (keeping you in the loop)-

Q1: What was the cause of death at the Colorado dairy farm?

The Weld County coroner’s office determined that hydrogen sulfide gas exposure caused the deaths of six workers at Prospect Valley Dairy.

Q2: Who were the victims in the dairy farm tragedy?

The victims included Alejandro Espinoza Cruz, his sons Oscar and Carlos, their relative Jorge Sanchez Pena, and two other workers, Ricardo Gomez Galvan and Noe Montañez Casañas.

Q3: What is hydrogen sulfide gas?

Hydrogen sulfide is a colorless gas that smells like rotten eggs. Prolonged exposure can cause unconsciousness and death within minutes.

Q4: What agency is investigating the dairy farm deaths?

The Occupational Safety and Health Administration (OSHA) is conducting the investigation, which could take several months to complete.

Q5: Are confined space deaths common in agriculture?

Yes. Farm workers face high risks in confined spaces like manure pits or tanks due to toxic gas accumulation and insufficient ventilation.