House Democrats on Wednesday subpoenaed Energy Secretary Rick Perry as part of the impeachment inquiry into President Trump. House Reps. Adam Schiff (D-CA), Elijah Cummings (D-MD), and Eliot Engel (D-NY) sent a letter to Perry, demanding key documents by Oct. 18. “Recently, public reports have raised questions about any role you may have played in conveying or reinforcing the President’s stark message to the Ukrainian President,” the chairmen wrote. “These reports have also raised significant questions about your efforts to press Ukrainian officials to change the management structure at a Ukrainian state-owned energy company to benefit individuals involved with Rudy Giuliani’s push to get Ukrainian officials to interfere in our 2020 election.”

In May, Perry led a U.S. delegation to Ukraine for President Volodymyr Zelensky’s inauguration. The energy secretary reportedly took the trip at the direction of Trump in place of Vice President Mike Pence. Perry’s presence appears to be in connection with a concerted effort by Trump allies to insert an American board member onto Ukraine’s multibillion-dollar oil and gas company, Naftogaz. The former Texas governor reportedly floated several oil executives from his home state to take the board position, including one of his former political donors. Trump has tried to blame Perry for the July phone call with Zelensky that instigated the whistleblower complaint.