Federal investigators have uncovered what they describe as a sweeping network of kickbacks, bribes and fraud involving at least eight employees and subcontractors of KBR, the former Halliburton subsidiary, in a scheme to inflate charges for flying freight into Iraq in support of the war, according to court papers unsealed yesterday.

The latest conviction in the cases related to the scheme came yesterday, when a former Houston-based executive for an air-freight carrier hired by KBR pleaded guilty in federal district court to dispensing bribes and then lying to federal investigators. The executive, Kevin Andre Smoot, 43, of The Woodlands, Tex., served as a managing director for Eagle Global Logistics Incorporated, a carrier that received a subcontract from KBR to ship the freight.

The guilty plea by Mr. Smoot is the second by an Eagle executive in the case. But the papers describing his plea indicate that investigators believe at least one more Eagle employee and five KBR employees, all so far unnamed, were also involved. Mr. Smoot alone admitted to delivering bribes, called gratuities in the legalistic language of the court papers, to the employees of KBR on some 90 occasions between 2002 and 2005.

At the core of the case is a contract that KBR, previously known as Kellogg, Brown & Root, won before the war to supply the American military with food, fuel, housing and other necessities. The value of the contract soared with the Iraq invasion, and has so far paid KBR some $20 billion.