House Oversight Committee leaders have asked Gov. Rick Snyder, R-Mich., to clarify when he learned that water in Flint, Mich., contained Legionnaire's disease after his aide testified earlier this week about a different timeline.

Chairman Trey Gowdy, R-S.C., and ranking Democrat Elijah Cummings of Maryland sent Snyder a letter Thursday asking him why he told Congress in March 2016 that he did not learn of the concern "until 2016."

"On October 6, 2017, one of your aides, Harvey Hollins III, provided testimony in the preliminary hearing for Nick Lyon. In that testimony, Mr. Hollins stated he called you in December of 2015 and made you aware of the outbreak of Legionnaires' disease," the letter states. "Mr. Hollins testified he made this call after a meeting of the Flint Water Advisory Task Force that occurred just prior to Christmas."

In Snyder's testimony, he said he held a press conference the day after learning of the disease's presence.

"In order to resolve this discrepancy in recollection, please supply the Committee with any additional relevant information you have concerning the date upon which you first learned of the Legionnaire's disease. If necessary, you may also choose to amend or supplement your testimony," the committee asked.

The committee gave Snyder an Oct. 25 deadline and included a warning to Snyder against perjury, lies under oath, corrupts the law or impedes an investigation.