Alexis, who had a prior record of weapon-related arrests during his time in the Navy, was killed by police during the shootout.
Defense officials say Alexis obtained a security clearance while he was in the Navy and was not subjected to a second background check when he became a contractor after leaving the service in 2011.
A Pentagon Inspector General report, released Tuesday, found that 52 felons had received unauthorized access to military facilities for 62 to 1,035 days, placing “military personnel, dependents, civilians, and installations at an increased security risk.”
The report also found convicted felons received access to bases because Eid Passport, the private firm conducting the background checks, did not identify the felony convictions in initial public records checks.
Sen. Dianne Feinstein (D-Calif.), head of the Senate intelligence committee, said Wednesday the panel planned to hold hearings on the security clearance process.
The California Democrat had demanded clearance reform earlier this year, in the aftermath of the illegal intelligence disclosures by former National Security Agency contractor Edward Snowden.
But the Pentagon remains adamant that sufficient checks are in place to ensure all clearance investigations are up to par, even if conducted by private firms.
"Its not just suitability check," the official said, noting the DOD review of clearance investigations.
"All of the components of the investigation" are reviewed by Pentagon, from the OPM findings to how the particular investigation was conducted.
If any discrepancies are found in that review, the case is sent back to OPM for further investigation, the official said.