The White House announced on Tuesday that the Obama administration was reviewing security procedures for government contractors after authorities said a private contract worker was responsible for the mass shooting at the Washington Navy Yard.

"At the president's direction, OMB is examining standards for contractors and employees across federal agencies," White House press secretary Jay Carney said.

The president had already ordered a review of government contractors by his Director of National Intelligence after National Security Agency leaker Edward Snowden disclosed classified details about U.S. phone and Internet surveillance programs.

Aaron Alexis, the 34-year-old whom authorities say shot and killed 12 people at the Navy Yard, had a history of mental illness and violent outbursts — he was arrested twice for gun-related crimes. Still, Alexis had proper clearance to enter the federal military post.

On Capitol Hill, lawmakers are also calling for a review of security-clearance rules for private contractors, expressing concerns about a wide network of employees with access to sensitive information and government locations.

The Navy is already looking into security practices at all its facilities.

Obama is receiving a briefing Tuesday afternoon from Attorney General Eric Holder and FBI Director James Comey about the Navy Yard shooting.