SPRINGFIELD, Ill. (NewsNation Now) —  Democratic county leaders in Illinois want an investigation of Republican state Rep. Chris Miller after he displayed a decal of an anti-government militia movement on his pickup truck parked at the U.S. Capitol during the deadly insurrection in January.

The Illinois Democratic County Chairs’ Association asked for a state investigation Friday after photos of Miller’s truck with a sticker for the Three Percenters surfaced on social media.

Miller, a cattle farmer first elected in 2018, denied involvement with the group. He was in Washington, D.C., for former President Donald Trump’s speech on Jan. 6.

“I have never been a member of the 3 percenters,” state representative Chris Miller (R-Oakland, Ill.) said in an email, before distancing himself from — and defending — the group.

A day earlier, Miller’s wife, freshman U.S. Rep. Mary Miller delivered a speech quoting Adolf Hitler that drew wide outrage.

“My son received the sticker that was on my truck from a family friend who said that it represented patriotism and love of country,” Miller, of Oakland, said in a statement. “I have since removed the sticker.”

Still, Kristina Zahorik, leader of the county chairs, submitted a request to the Office of the Legislative Inspector General to investigate Miller’s actions during the Jan. 6 insurrection.

“Miller’s attendance at the rally that turned into a mob and insurrection of our nation’s Capitol is troubling, and to date, many unanswered questions remain about his subsequent actions and whereabouts that day,” Zahorik said.

Republican U.S. Rep. Adam Kinzinger of Illinois, who was among 10 GOP House members to vote to impeach Trump, said he supported looking further at the matter.

“Rep. Miller put a militia sticker on his car and is suspected to have been at the insurrection,” Kinzinger wrote on Twitter. “Our party needs to handle this and I support further investigation.”

Recent reports revealed other militia groups, such as the Oath Keepers, were deeply involved in plotting the January 6th riots. Some have faced criminal prosecution.

The Associate Press and NewsNation WCIA affiliate contributed to this report.