(CNN) House intelligence committee members on Thursday interviewed a former Justice Department official who oversaw the National Security Agency's surveillance program, as part of their Russia probe.

Members interviewed former assistant Attorney General John Carlin -- a key figure in former President Barack Obama's Justice Department -- according to Rep. Mike Conaway, the Texas Republican leading the House investigation.

Republican lawmakers in particular have been interested in probing whether Obama administration officials illegally revealed or "unmasked" the names of people on the Trump transition team. Former Obama national security adviser Susan Rice had been scheduled to testify before the House intelligence committee earlier this month, but was rescheduled.

House intelligence committee Chairman Devin Nunes is conducting a separate probe into "unmasking" -- or identifying of names in intelligence reports -- but Thursday's interview of Carlin was not in connection with that part of the investigation, Conaway said.