(Polson, Mont.)-Senator Jon Tester today is pushing the National Security Agency (NSA) for more answers following the latest failure in the security clearance background check process.

In a letter to NSA Director Admiral Michael Rogers, Tester expressed his frustration that once again U.S. national security was jeopardized due to significant gaps that exist in the security clearance process.

"Just as Chelsea Manning, Edward Snowden, and Navy Yard Shooter Aaron Alexis exposed the severe vulnerabilities in our security clearance system, it is important that we find out how to best shore up these gaps in order to preserve American security," Tester wrote. "I am concerned that the process of this vetting - or lack thereof - may have once again expose the vulnerabilities of our security clearance process to insider threats and, absent serious reforms, will continue to haunt U.S. intelligence agencies for years to come."

Last week, Harold T. Martin III was arrested and charged with stealing top secret data from the NSA. News reports indicated that Martin may have been removed from a position at the NSA and placed in a new job at the Defense Department without having his clearance re-examined.

In his letter to Admiral Rogers, Tester requested information on a series of concerns regarding Martin's actions-including which agency was responsible for conducting Martin's security clearance background check and why Martin had access to the files he is alleged to have stolen.

Tester has been a leading voice in the Senate regarding security clearance reforms, and he successfully included provisions in the 2016 NDAA that reformed how criminal history records are shared between law enforcement agencies and background investigators.

Tester is also sponsoring the Security Clearance Accountability, Reform, and Enhancement (SCARE) Act, which prohibits federal contractors and employees who have compromised the integrity of a background investigation from performing them in the future.

In 2014, Tester's Security Clearance Oversight Reform (SCORE) Act was signed into law and allows the Inspector General of the Office of Personnel Management (OPM) to use resources from the agency's $2 billion Revolving Fund to more thoroughly investigate cases where the integrity of the background check process may have been compromised.

In August, Tester and Senator Claire McCaskill (D-Mo.) sent a letter to OPM Director Beth Cobert demanding answers about how the new National Background Investigations Bureau would better keep our nation's most sensitive information and places secure.

Tester's letter to Admiral Rogers is available HERE.