Deadly methane gas emanating from a dairy farm's manure pit in Virginia killed five people, including four members of a Mennonite family, US authorities said.
Emergency workers speculate that after the first victim was overcome at the Showalters' dairy farm in the Briery Branch community yesterday, the others climbed into the pit in a frantic rescue attempt.
"It was a domino effect with one person going in, the second person going after them," Rockingham County Sheriff Don Farley said.
Scott Showalter, his wife Phyllis and their two daughters, aged nine and 11, were killed. The couple also had two younger daughters. A 24-year-old farm worker also died as he tried to save Mr Showalter, who fell into the pit while transferring manure.
The pipe that was transferring the manure became clogged, and Showalter climbed in the pit to fix the blockage, Farley said. "It was probably something he had done a hundred times," Farley said. "There was gas in there and he immediately succumbed."
Methane gas is an odourless and colourless byproduct of liquefied manure. The pit was nearly enclosed and poorly vented, Sheriff Farley said.
The Showalters milked 103 cows on their farm west of Harrisonburg in Virginia's Shenandoah Valley, an area dotted with church steeples and old-fashioned red barns.
There are more than 6,000 Mennonites in 40 churches in Rockingham County. The Showalters belonged to a church in a branch whose members shun many of the trappings of modern society but drive cars and have telephones.
AP