The White House was reportedly unaware that one of its senior staffers had testified before a grand jury as part of special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's investigation into Russian election meddling.

ABC News reported Thursday that White House officials learned that Sam Clovis had met with the grand jury only after it was reported by the news media. He reportedly testified regarding his role in President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE's 2016 campaign.

Mueller's interest in Clovis was revealed this week after a former foreign policy adviser to Trump's campaign, George PapadopoulosGeorge Demetrios PapadopoulosTale of two FBI cases: Clinton got warned, Trump got investigated Trump says he would consider pardons for those implicated in Mueller investigation New FBI document confirms the Trump campaign was investigated without justification MORE, pleaded guilty to lying to federal investigators about his interactions with a Kremlin-linked professor.

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Clovis, who currently serves as a senior White House adviser to the Department of Agriculture, was Papadopoulos's "campaign supervisor" on the Trump campaign, The Washington Post reported earlier this week. Clovis encouraged the young campaign adviser to engage with Russian contacts.

“The White House was surprised to learn Mr. Clovis had been contacted by the special counsel’s office as part of their separate probe of Mr. Papadopoulos’s activities," a source familiar with the probe told ABC News.

Clovis on Thursday withdrew from consideration to be the Agriculture Department's chief scientist amid mounting controversy related to his links to the Russia investigation. He had also been criticized for his general lack of science credentials.