A U.S. intelligence official alarmed by some undisclosed actions by President Donald Trump filed an official whistleblower complaint last month with the inspector general for the intelligence community, according to reporting from the Washington Post and New York Times. The Times, following an initial report related to Trump’s communications with a foreign leader, has reported that the whistleblower’s concerns dealt with multiple incidents—not just a single conversation with a world leader.

The Post reported on Thursday that the whistleblower was concerned in part with a “promise” Trump made to foreign leader, whose identity has not been released. The Post reported that the official found Trump’s verbal commitment “so troubling” that the official came forward. It’s not clear what form the interaction took place, though one intelligence official told the Post that it was a phone call. The Times’ report did not specify what any other “acts” in the complaint may have been.

Intelligence Community Inspector General Michael Atkinson found the complaint, which was filed on Aug. 12, to be credible and designated the matter of “urgent concern,” a legal classification that is supposed to prompt the notification of oversight committees in Congress. Acting Director of National Intelligence Joseph Maguire, however, has so far refused to share the whistleblower’s concerns with Congress, setting off yet another power struggle between congressional leaders and the Trump administration, as well as speculation over what leader Trump may have acted inappropriately with.

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According to the Post, White House records during the five weeks leading up to the August complaint show Trump interacted with at least five foreign leaders. Trump met with the leaders of Pakistan, the Netherlands, and Qatar at the White House during that time; received correspondence from North Korean leader Kim Jong-un; and, more notably, initiated a phone call with Russian President Vladimir Putin on July 31, less than two weeks before the complaint was filed. “The dispute is expected to escalate Thursday when Atkinson is scheduled to appear before the House Intelligence Committee in a classified session closed to the public,” the Post notes. “The hearing is the latest move by committee Chairman Adam B. Schiff (D-Calif.) to compel U.S. intelligence officials to disclose the full details of the whistleblower complaint to Congress.”

On Twitter, Trump denied any wrongdoing, arguing that nobody was “dumb enough to believe that I would say something inappropriate with a foreign leader while on such a potentially ‘heavily populated’ call.”