The charges come partly as the result of a raid by federal agents two years ago in which 22 weapons were seized, including 17 AK-47s.

Jackson left Blackwater, which is now known as Xe Services, last year. The company  has struggled to restore its image after a 2007 shooting in Baghdad which saw several of its guards charged with federal crimes.

That case was thrown out of court when a judge found that prosecutors had mishandled evidence, and so far the company's executives have escaped censure despite a range of investigations in the incidents involving its staff.