CHICAGO (CBS) – Federal investigators are looking at nearly four years of Cook County Commissioner William Beavers’ expense records.

On Wednesday, Beavers acknowledged that for two years, he used a government allowance to supplement his salary.

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The Chicago Sun-Times reported that several county commissioners have collected up to $1, 200 a month on top of their $85,000 base salary, through a contingency account that some opposing commissioners have deemed a “slush fund.” Commissioners who use the contingency account are required to file reports on how they spend the money.

Following an Internal Revenue Service investigation, grand jury subpoenas are asking for all of Beavers’ expense filings since he took office in 2006.

Beavers says he used the contingency allowance, but paid taxes on it.

Beavers, who has referred to himself as “The Hog with the Big Nuts,” was elected to the County Board in 2006, after serving 13 years as alderman of the South Side’s 7th Ward. He also served as a Chicago Police officer

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He served as a mentor to outgoing Cook County Board President Todd Stroger, after Stroger’s father, the late John Stroger, had to leave office after winning the 2006 Democratic primary due to a massive stroke.

A political deal that year gave the Democratic nomination for the board presidency that year to Todd Stroger, while Beavers was placed on the ballot for the 4th District County Board seat, which John Stroger had also held while board president.

When Cook County Clerk David Orr claimed that Beavers might have been understating the severity of John Stroger’s medical condition to keep independent candidates out of the 2006 race for County Board president, Beavers famously responded by calling Orr a “little poop butt.”

John Stroger died in 2008. Todd Stroger was defeated by Ald. Toni Preckwinkle (4th) in the Democratic primary this past February.

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When Beavers left his City Council seat, his daughter, Darcel Beavers, took his place. Darcel Beavers was in turn defeated by Sandi Jackson, the wife of U.S. Rep. Jesse Jackson Jr. (D-Ill.)