A lawyer for the cooperative, F. Mark Hansen, confirmed that the IRS served it with a sealed warrant seeking account records.
"They're giving their full cooperation and they're providing access to what ever files, computer records," Hansen said.
"I am informed there is nothing to hide," he added.
A copy of what appeared to be a federal search warrant with the word "Sealed" written across the top sat on the passenger seat of his car as he spoke to reporters. Hansen declined to provide a copy to The Salt Lake Tribune.
Law enforcement also conducted a raid in Sandy at the home of Jacob Kingston, one of the owners of Washakie Renewable Energy.
Contacted Wednesday, company officials said the nature of the action was not clear.
"We do not have an official comment and it will stay that way until we have a better understanding of the situation," said Washakie's general counsel, Jason Foulger.
Law enforcement apparently did not raid the Washakie plant itself, located in Plymouth, 100 miles north of Salt Lake City. Box Elder County Sheriff's Chief Deputy Dale Ward said that office had been told search warrants would be served, then received a call Tuesday saying the warrants had fallen through.
Kingston sons Jacob and Isaiah built the Washakie plant in 2008 to turn oilseed such as canola and soy into biodiesel. Washakie has become a frequent advertiser during Utah Jazz broadcasts and before movies shown at Megaplex Theatres.
But according to court records, the plant did not reliably produce. Apparently it was more successful at collecting federal subsidies intended to promote production of alternative fuels, even when it wasn't producing these products.
Between January and October 2010, a period when the plant failed to produce any biofuels, it reaped $2 million in credits based on 7.2 million gallons that someone else produced, according to a notice of violation filed by federal regulators in 2011.
Later that year, however, the U.S. Department of Agriculture's Rural Development Office extended the company a $496,750 grant, observing Washakie's process could help reduce U.S. dependence on foreign oil.
Last year, Washakie agreed to a $3 million fine to resolve these allegations. Former employees who asked to not be named said the plant was still not producing as of six months ago.
In a 2011 Rolling Stone interview, then-Attorney General Mark Shurtleff described the Kingstons as an "organized-crime family."
Despite this troubling history, current Attorney General Sean Reyes has accepted $31,000 from Washakie and its executive Sally Kingston, Jacob's wife, according to campaign finance disclosures.
"We were unaware of any investigation of the company and we are still unaware of the allegations being filed," said Alan Crooks, general consultant for Reyes' election campaign. "If there is any wrongdoing proved to be true, we would return the funds or set up a charitable organization to return the money to the community. We don't know very much right now."
Besides the Kingston Group and the Davis County Cooperative, the sect is also known as the Latter Day Church of Christ. Unlike Utah's better-known polygamous sect, the Fundamentalist Church of Jesus Christ of Latter-Day Saints, the Kingstons are integrated into the Wasatch Front. They wear conventional clothing, and members own perhaps hundreds of businesses, from Washakie Energy to refuse companies to management firms. The sect has its own banking system for members.
The group is said to be led by Paul E. Kingston. A brother, John Daniel Kingston, gained notoriety for forcing teenage female members into marriages with older relatives. In 1999, he was sentenced to 28 weeks in jail for beating a 17-year-old daughter who refused to submit to a marriage to her uncle.
In 2004, Jeremy Ortell Kingston was sentenced to a year in jail for "marrying" and having sex with a 15-year-old cousin.
And in 1999, David Ortell Kingston Jeremy Kingston's uncle was sentenced to the Utah State Prison for up to 10 years for committing incest with the 16-year-old niece who became his 15th wife. David Kingston was released from prison in 2003.
In recent years, former members have lobbied for law enforcement to take action against the sect. Three sisters who left the sect are the stars of a reality television show called "Escaping Polygamy."
Two of the stars, half-sisters who go only by the names Jessica and Shanell, were at the South Salt Lake scene Wednesday with a camera crew. They said they had no advance notice of the raid and declined to answer any more questions.
Last year www.kingstonclan.com went online. It accuses Kingston leaders of various crimes.
Twitter: @natecarlisle, @brianmaffly