A senator has opened the door to using a subpoena to get answers from a key national security agency about the breach of the Office of Personnel Management.

Sen. Ron Wyden, D-Ore., sent a letter to the National Counterintelligence and Security Center on Aug. 12 asking the agency whether it had identified U.S. security clearances as a potential target for foreign intelligence and if it had informed the OPM of that fact. He also asked whether there was a reason for the OPM to retain security clearance information as far back as 1985.