Authorities say a manure holding tank's "deadly dome of air" was responsible for the deaths of a Wisconsin farmer and 13 of his cows on Aug. 15.
"I know of 13 dead cows," said Portage County Coroner Scott Rifleman, WAOW reports. "There were others that were sick. I am unsure if any more died. The family is devastated, absolutely devastated.”
Workers found the body of the 29-year-old farmer, Michael Biadasz, who owned the farm near Amherst with his father, when they came to start work for the day.
It is believed that either methane or sulfur oxide fumes combined with warm air that killed the man and cows, but investigations are still ongoing.
Many posted their sympathies for the family on social media.
"As if there isn't already enough danger in the lives of farmers, this family had to suffer this freaky accident," wrote Alice Ojala-Johnson on WKOW's Facebook post about the incident. "So sad."
Another woman said she was one of Biadasz's classmates.
"Went to high school with Mike - he was a great guy! So sad, may he rest in peace," Jenni Welp wrote.
Others say tougher rules are needed on holding tanks to prevent this type of incident.
According to the National Ag Safety Database, increased use of toxic gases has led to the deaths of many.
"The four main gases produced from decomposing manure are Hydrogen Sulfide, Methane, Ammonia, and Carbon Dioxide," writes NASD. "In high concentrations, each of these gases may pose a health threat to humans and livestock."
"In animal housing facilities, where the manure pit is often located below the facility floor, manure gases are generally detectable in low concentrations throughout the year," it notes. "When pits are agitated for pumping, some or all of these gases are rapidly released from the manure and may reach toxic levels or displace oxygen, increasing the risk to humans and livestock."
NASD's website offers a list of guidelines farmers should follow to keep safe, ranging from maintaining adequate ventilation where animals are stored to posting warning signs.
"In addition to adhering to proper construction and maintenance procedures for liquid manure storage facilities, owners should be encouraged to follow a few precautionary measures to protect both workers and livestock from harmful manure gases," NASD writes.