Senate Republicans are asking the FBI to look into whether Colin Kahl sought or disclosed classified information after leaving the Obama administration, The Hill reported. Kahl’s nomination to become undersecretary of defense for policy has been stalled as he faces Republicans’ apparent unity against his confirmation.

Republicans are now pointing to a series of tweets from Kahl in 2017. In written responses to the Senate Armed Services Committee, Kahl said the tweets were based on information in a Washington Post article, but his critics charge that he shared more information than could be found in the article.

“These disclosures are extremely concerning and warrant a complete FBI investigation to determine the full scope of the nominee’s mishandling of sensitive national security information, apparently for his own perceived political gain,” Sen. Bill Hagerty (R-Tenn.) told The Hill.

Former federal prosecutor and Justice Department official David Laufman told Politico that his “antennae are up” because the investigation request letter was signed only by Republicans.

“That doesn’t speak to the merits of whether there was a violation of law. It’s great that these members of Congress are concerned about it,” Laufman said. “The real question is whether the agency that owns the information at issue is concerned about it. Have they filed a crimes report?”

Republicans have also raised concerns about Kahl’s role in Obama-era policy toward Iran.

Air National Guard photo of Sen. Bill Hagerty by Tech. Sgt. Mark Thompson