An Arizona Republic feature earlier this summer has led to an FBI inquiry into Arizona governor Doug Ducey’s current and former staffers — one of whom is a federal judge — over a $100 million tax break for one of the governor’s powerful campaign advocates.

In another headache for the governor following blowback on his efforts to withhold federal grant money from Arizona schools, the FBI’s Public Corruption Unit has kicked off a new investigation into some of his present and past associates. This follows the Republic’s reporting on efforts to push the Arizona Department of Revenue to refund sales taxes on fuel that are in place for mining companies.

According to the Republic, 16 separate meetings took place between Ducey officials and the Department of Revenue with the goal of thrashing out a deal and getting Revenue officials to drop their opposition to the refund. One refund being issued to one fuel company would have started a chain effect, triggering across-the-board refunds in similar cases and ultimately costing the state of Arizona roughly $100 million.

Texas-based tax firm Ryan LLC represented many of the mining companies and stood to benefit immensely from the proposed agreement. G. Brint Ryan, a Ducey supporter and a major GOP donor, is the founder of Ryan LLC.

In the end, Attorney General Mark Brnovich convinced an appeals court to rule against Ryan’s clients — who stood to make a fortune from an agreement that was being privately, doggedly pursued over many months.

However, the FBI has opened an investigation anyway, though Ducey claimed Tuesday he had no knowledge of it.