As former national security adviser Michael Flynn comes under increasing security over his conversations with the Russian ambassador before inauguration, House Oversight Committee Chair Jason Chaffetz (R-UT) joined an inquiry launched by Democrats into Flynn’s 2015 speaking engagements in Russia.

The committee’s ranking member, Rep. Elijah Cummings (D-MD) and other House Democrats sent a letter to the Defense Department earlier in February asking for information on whether Flynn received payment from Russian officials for attending a dinner hosted by Kremnlin-backed outlet Russia Today. The Democrats charged that Flynn may have violated the Emoluments Clause, which bars government officials from receiving payments from a foreign government.

However, the Pentagon responded this week to inform House members that they do not have any records showing that Flynn requested permission to attend the speaking engagement or documenting payments Flynn received, according to a new letter from the House Oversight Committee.

On Thursday, Chaffetz joined Cummings in writing a letter to a speaking bureau, Leading Authorities, asking for information on Flynn’s trip, specifically whether he received payment from a foreign government.

The letter signed by Chaffetz comes after he declined to investigate communications between Trump aides and Russian officials in the Oversight Committee. The oversight chair did ask the Justice Department’s inspector general to investigate leaks to the media about Trump associates’ calls with Russian officials.