The inquiry will focus on Boeing initially but is likely to look at other big defense contractors such as Lockheed Martin and Carlyle Group, the paper said, quoting people familiar with the matter.

"Investigators want to determine whether dozens of other Defense Department officials complied with federal requirements to refrain from participating in certain program decisions both before and after they made their moves to the private sector," the Journal said.

In December, the Pentagon suspended a multi-billion dollar tanker aircraft contract with Boeing following revelations about the company's improper recruitment of an Air Force official.

Boeing fired the official in question, former head of Air Force purchasing Darleen Druyun, and chief financial officer Mike Sears, in late November. CEO Phil Condit resigned shortly thereafter.

Boeing is also facing an investigation in St Louis, Missouri for allegedly using foreign titanium in F-15 fighter jets and other Pentagon programs, which is against US law, the Journal said.

It is also under investigation and facing possible penalties for obtaining Lockheed Martin documents when the two firms were competing for a Pentagon contract.

WAR.WIRE