"We are so reliant on military contractors" that the vetting is key to our national security, Sen. Susan Collins told CNN.
Collins, a Republican who serves on the Senate Intelligence Committee, said she now questions "the kind of vetting contractors do."
Washington needs a lot more answers," Rep. Eleanor Holmes Norton, D-District of Columbia, told CNN Tuesday.
Sen. Kelly Ayotte, R-New Hampshire, is asking for a hearing to examine problems the shooting at the Navy Yard highlighted.
"In the wake of this tragedy, we must thoroughly review and fix deficiencies within existing federal contracting hiring practices that the alleged Washington Navy Yard gunman exposed and exploited to ensure the safety of the rest of our service family---servicemembers, civilian workers, and contractors, alike," Ayotte said.
Government relies on contractors
In the 12 years since the September 11 attacks, the United States has ramped up contracting to support new defense and intelligence efforts.
And contractors are a major reason the federal government can operate today as its workforce shrinks.
According to statistics, last year it spent more than $500 billion -- or roughly 14% of the federal budget -- on private-sector contracts.
That doesn't include many contracts awarded by the National Security Agency and other intelligence agencies, which keep their spending classified.
There are already moves in Congress to tighten the security clearance system.
Sen. Bill Nelson, D-Florida is a co-sponsor of a bill to force government agencies asking for the background checks of potential clearance holders to increase oversight and to fire investigators who falsify those investigations.
Because of the rise in number of contractors, federal agencies often farm out background check investigations before deciding whether to grant security clearance. While the process is supposed to be the same whether it is done by a government or private sector employee, some experts question whether that is the case.
One of the largest private firms that specializes in these investigations, USIS, which did former NSA contractor Edward Snowden's background check, is under investigation, according to an official from the Office of Personnel Management who testified before Congress in June.
Sen. Claire McCaskill, D-Missouri, said at the hearing her staff had been informed of the company's "systemic failure to adequately conduct investments under its contract" with OPM. USIS has not commented on the investigation.
Broader review planned
The issue of contractors also has the attention of the Obama administration.
Because of the leaks from Snowden, the Director of National Intelligence was already examining who should have access to classified materials. Now officials say there will be a broader review of contractors and employees across all federal agencies. This review will look at the oversight, nature and implementation of security protections as well as looking at whether these employees and contractors are suited to work for the federal government, an administration official told CNN.
"I can tell you at the President's direction (the Office of Management and Budget) is examining standards for contractors and employees across federal agencies. So this is obviously a matter the President believes and has believed merits review," White House Press Secretary Jay Carney told reporters Tuesday.
Stan Soloway, president and CEO of the Professional Services Council -- the trade association for contractors -- told CNN that "contract employees and government employees go through the same process."