(CNN) Treasury Secretary Steve Mnuchin will brief House lawmakers on Thursday afternoon about the Treasury Department's decision to ease sanctions on companies tied to Russian oligarch Oleg Deripaska, according to two Democratic sources.

The briefing marks a first step toward tougher oversight of the Trump administration on Russia-related matters. It comes as Democrats mull whether to formally push back against the sanctions relief for the Russian companies, announced last month.

The Treasury Department moved to impose sanctions last April on Rusal, the world's second-largest aluminum producer, as well as EN+ Group, the company that holds Deripaska's stake in both Rusal and GAZ Group, a Russian automotive conglomerate.

Treasury said in a statement that both companies had made "significant restructuring and corporate governance changes."

Treasury officials did not respond to a request for comment on Thursday's briefing.

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