Michael Flynn, seen here arriving for a news conference in the East Room of the White House in February, is being investigated by the inspector general of the Department of Defense, Rep. Elijah Cummings said Thursday. Evan Vucci/AP hide caption

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Evan Vucci/AP

House Oversight Committee Chairman Jason Chaffetz, R-Utah (right), and ranking member Rep. Elijah Cummings, D-Md., speak to reporters about Michael Flynn, President Trump's former national security adviser, on Tuesday in Washington, D.C. Win McNamee/Getty Images hide caption

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Win McNamee/Getty Images

Former IRS official Lois Lerner raises her hand as she's sworn in Wednesday at the start of a House Oversight & Government Reform Committee hearing. She declined to answer questions posed by Chairman Darrell Issa, invoking her Fifth Amendment right. Chip Somodevilla/Getty Images hide caption

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Chip Somodevilla/Getty Images

Rep. Elijah Cummings, D-Md., gestures as he speaks in an Oversight Committee hearing on Capitol Hill in May 22. Carolyn Kaster/AP hide caption

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Carolyn Kaster/AP

It would be a vast understatement to say that Republican Rep. Darrell Issa (right) of California and Democratic Rep. Elijah Cummings of Maryland don't see eye to eye on the IRS scandal's latest development. J. Scott Applewhite/AP hide caption

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J. Scott Applewhite/AP