Treasury Secretary Steven Mnuchin’s decision to ease sanctions on companies affiliated with a blacklisted Russian oligarch has drawn skepticism from congressional Democrats, a new letter shows.

A group of seven Democratic committee chairs are questioning the Treasury Department’s agreement to lift sanctions on three companies owned by oligarch Oleg Deripaska, who was sanctioned for his relationship with Russian President Vladimir Putin and “has abetted the Putin Regime’s malign activity against the United States,” as they put it. The letter marks the first act of oversight related to Russia policy for the Foreign Affairs Chairman Eliot Engel since the New York Democrat took over the panel this week.