White House Deputy National Security Adviser Ben Rhodes has become the subject of a congressional probe into whether FBI officials declined to grant him an interim security clearance for use during President Obama’s transition.

In a letter sent to FBI Director James Comey in mid-December, Republican Congressmen Trent Franks, Ariz., and Jim Bridenstine, Okla., pressed the agency for details about Obama’s top national security aide and his clearance investigation. The letter, first reported by the Washington Free Beacon, questions about whether Rhodes’ access to classified information is inappropriate considering FBI officials may have been perturbed by his past.