Two witnesses in the House impeachment probe told investigators last month that White House Chief of Staff Mick Mulvaney was directly involved in efforts to push Ukraine to undertake particular investigations in exchange for a presidential meeting.

Fiona Hill, the former top Russia advisor to Trump, and Lt. Colonel Alexander Vindman, director for Eurasian affairs at the State Department, told House investigators that Mulvaney coordinated with EU Ambassador Gordon Sondland on delivering the message to Ukraine that President Volodymyr Zelensky would not get a meeting with President Donald Trump unless his officials opened up probes into Hunter Biden, the gas company on whose board he sat, and the 2016 presidential election. The testimonies mark the most direct link between the scandal now imperiling the presidency and the president’s chief of staff.

In her testimony, Hill provides investigators details about a July 10 meeting at the White House with former National Security Adviser John Bolton, Sondland, Energy Secretary Rick Perry, former top diplomat for Ukraine Kurt Volker and Ukrainian politicians, including Chairman for the National Security and Defense Council of Ukraine Oleksandr Danylyuk and a top aid to Zelensky Andre Yermak.

Recounting the episode to investigators, Hill says Bolton “stiffened” and ended the meeting early following a remark by Sondland that called for “deliverables” —i.e. investigations—in Ukraine in exchange for a meeting.

Hill said Sondland “blurted out” that there was “an agreement with the Chief of Staff for a meeting if these 'investigations in the energy sector start.’”

Sondland repeated that line in a follow-up meeting with the Ukrainians minutes later in the Ward Room of the White House, Hill said. She added that her director for Ukraine was “completely alarmed” as were the Ukrainians in the room, particularly Danylyuk. Bolton had sent Hill to the Ward Room to take note of what Sondland was conveying to the Ukrainians and told her to tell the White House Counsel’s office that he was “not part of whatever drug deal Sondland and Mulvaney are cooking up on this.”

Hill said Sondland had told her in late June that he was “in charge” of the Ukraine portfolio.

“And I asked, well, on whose authority? And he said, the President,” Hill said.

Vindman was also in the series of meetings Hill referenced and took note of Sondland’s mention of Mulvaney as well. In his deposition, he told investigators that “Sondland relatively quickly went into outlining how the -- you know, these investigations need to -- on the deliverable for these investigations in order to secure this meeting.”

When asked how Sondland came to believe the “deliverable” was necessary, Vindman said: “I heard him say that this had been coordinated with White House Chief of Staff Mr. Mick Mulvaney.”

Mulvaney has declined to be interviewed by congressional investigators about his involvement in the Ukrainian affair, including ignoring a subpoena for an appearance before the committee on Friday. He had been tied to the matter most through his post as chair of the Office of Management and Budget, which effectively placed a hold on the military aid to Ukraine that was allegedly done to encourage Zelensky to initiate those investigations.

But Mulvaney also infamously took to the White House press briefing room several weeks back to defend the very notion that quid-pro-quos were legally permissible in conducting U.S. foreign policy—only to subsequently deny that he’d made such a statement at all.