An independent review of the security clearance process released six months after the Navy Yard shooting finds the U.S. government has exposed classified national security information, often at very sensitive levels, to far too many people.

It also concurs with the findings of a House Oversight and Government Reform Committee report that suggested the tragedy could have been prevented.

Officials at the Pentagon said Tuesday that the Department of Defense approaches security from a perimeter perspective, rather than looking at insider threats. They suggest the government should subject security-clearance holders to more intense scrutiny and try to trim the number of people with access to the nation’s most sensitive information.

“Far too many people have security clearances,” said Paul N. Stockton, a former assistant secretary of defense for homeland security who was part of the independent panel appointed by the DOD in the wake of the Sept. 16 shooting.

Since 9/11, the number has “tripled,” Stockton said.

The White House also released its own report on security clearance procedures, following a 120-day review ordered by President Barack Obama in the wake of the Navy Yard shooting.

The increase in the number of security clearances has significantly increased risks and costs to the government, according to the review led by the Office of Management and Budget. For the DOD, the number of top secret security clearance investigations increased 42 percent between 2005 and 2013, resulting in an increase of more $179 million in program costs.

As a result, the administration is recommending reducing the number of people with security clearances by 10 percent. Federal agencies should review their positions to validate that each government employee or contractor who has been deemed eligible for a security clearance actually needs access to classified information.

Officials are also suggesting that the DOD and other federal agencies reconsider whether they want to continue depending on the Office of Personnel Management to conduct background investigations. They recommend looking at other models, including the State Department’s internal approach.

House lawmakers expressed concern about the OPM’s background investigation work during a Feb. 11 Oversight and Government Reform panel examining the Southeast D.C. shooting that rocked the Capitol community. The recommendations released Tuesday call on state and local law enforcement officers to give the federal government better access to criminal records, another suggestion made during the hearing.

Rep. Darrell Issa, R-Calif., who serves as House Oversight and Government Reform chairman, said the DOD report concurs with the committee’s findings.

“The Department and the Committee both concluded that Aaron Alexis could have been stopped and his clearance could have been pulled before the Navy Yard shooting if all information available was properly obtained and reported,” Issa said in a statement on the DOD report.

Rep. Elijah E. Cummings, D-Md., ranking member of the committee, commended the Obama administration for implementing continuous evaluation of security clearance holders and strengthening the information-sharing relationship with local and state law enforcement.

Still, Cummings sees more room for improvement.

He said in a statement that the recommendations “do not go far enough to detect false information submitted by applicants like Aaron Alexis.

“I believe that judging the truthfulness of applicants in subject interviews and for top secret clearances is an inherently governmental function with grave national security implications, and it must be federalized.”

Cummings and Rep. Stephen F. Lynch, D-Mass., are co-sponsoring legislation to insource those functions.

The findings also suggest eliminating the periodic review process that currently mandates security clearances be reviewed every 5, 10 or 15 years, and replacing it with a continuous evaluation system. It would screen holders of federal security clearances in real time, with the help of a government-wide information technology strategy. To help make the recommendations suggested, the Obama administration has established a team to coordinate efforts across the federal government.

During the Pentagon press conference, Navy Secretary Ray Mabus reflected on the day, almost exactly six months ago, that he visited building 197 — where 12 Navy civilian and contractor personnel had been slain — and found an “overwhelming” number of employees, including some who were injured during the shooting, already back at work.

Mabus said the “danger posed by an insider threat is insidious.

“In an office building near our nation’s capitol,” he continued, “it’s almost incomprehensible.”