MADISON, Wis. (AP) — The Wisconsin Department of Justice confirmed Thursday that its criminal investigators are looking into the removal of Wausau’s only absentee ballot drop box by the mayor last month.

The Marathon County district attorney had asked for assistance from DOJ about the incident in the small city about 200 miles northwest of Milwaukee. The department’s Division of Criminal Investigation will take the lead, said the agency’s spokesperson Gillian Drummond.

Mayor Doug Diny removed the city’s drop box on Sept. 22 without consulting with the clerk, who has the authority under a Wisconsin Supreme Court ruling to make one available. They are not mandatory in the state.

Diny, who ran as a conservative and opponent of drop boxes in the nonpartisan mayor’s race, has said he wanted the city council to discuss whether to use a drop box. The council is scheduled to discuss the issue at a meeting Tuesday.

The mayor turned the box back over to the clerk, who had it installed and bolted to the ground on Monday.

The box was locked and no ballots were in it when the mayor took it. City workers planned to bolt it to the ground but did not have a chance to do it before the mayor, wearing a hard hat and posing for pictures he later distributed, wheeled it away.

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The mayor insists he did nothing wrong. Drop box supporters are calling for a federal investigation, saying Diny broke federal law by interfering with the right to vote.

More than 60 towns, villages and cities in nine counties have opted out of using the boxes for the presidential election in November, according to a tally by the group All Voting is Local. Drop boxes are being embraced in heavily Democratic cities, including Milwaukee and Madison.

Wausau, with about 40,000 people, was among the cities that did not use an absentee drop box in the August state primary. Wausau is located in Marathon County, which Republican former President Donald Trump won by 18 points in both 2016 and 2020.