The House Foreign Affairs Committee requested materials regarding potential threats to former U.S. Ambassador to Ukraine Marie Yovanovitch’s safety after messages turned over to Congress suggest that she may have been surveilled. In a Wednesday letter to the undersecretary of state for management, Chairman Eliot Engel (D-NY) wrote that he was “deeply concerned” about the apparent efforts of Rudy Giuliani associate Lev Parnas and Robert Hyde to watch and potentially threaten Yovanovitch while she was still the ambassador. Engel said messages, which contained sensitive information about Yovanovitch’s whereabouts and her security protocols, implied that someone was providing real-time information to both Hyde and Parnas about the then-ambassador. “I cannot overstate the profound security risk that this poses to the U.S. mission and our interests in Ukraine,” Engel wrote. He requested any and all documents relating to Parnas, Hyde, and threats against personnel at the U.S. Embassy in Kyiv be turned over to the committee by Jan. 23.

The request comes after Giuliani admitted to pushing Yovanovitch out of Ukraine as he—along with Parnas and others—was involved in an effort to dig up dirt on former Vice President Joe Biden and his son in Ukraine.