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An Internal Revenue Service watchdog on Friday said he informed Obama administration officials last June, in the heat of the 2012 election season, that a probe was under way over the agency's targeting of conservative groups.

J. Russell George, Treasury inspector general for tax administration, said Friday at the first congressional hearing on the matter that he told Treasury Deputy Secretary Neal Wolin that the inspector general's office was conducting a review sometime around June 2012. Mr. George said he informed Mr. Wolin of the existence of the investigation but not the findings.

After the hearing, a spokesman for Mr. George's office said the Treasury's general counsel was told that the inspector general's office was looking in to the matter on June 4 of last year, and that Mr. Wolin was informed a short time later.

The revelation, one of the few new details to come from a House Ways and Means Committee hearing on the IRS controversy, suggests administration officials may have known about the practice earlier than was previously disclosed. The inspector general's investigation had only begun in March 2012, so the review would have been at an early stage.

Treasury officials on Friday didn't immediately respond to questions about what Mr. Wolin learned from the conversation or what he did with that information.

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