The state attorney general's office said in a news release that Allen Ray ran a fake company to which road work money funneled.
Prosecutors say former DOT signal shop director Curtis Singleton demanded contractors give him bribes of around $1,500 each and told a contractor to keep working the contractor needed to give him a deal on a new truck.
Prosecutors say former DOT inspector Joe Butler illegally sold agency equipment worth tens of thousands of dollars and kept some money for himself.
All three men pleaded guilty Monday. A fourth, Charles Shirley, died after being indicted.
The men will be sentenced later and must cooperate with any ongoing investigation.
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