Stewart, a former agent for the Bureau of Diplomatic Security, gathers intelligence on the cartels for Stratfor, a Texas-based security consulting firm that helped document Guzman's worth.

CNN: Stakes rise as drug war threatens to cross border

Unnamed officials speaking to the New York Times questioned whether Bureau of Diplomatic Security officials had the authority to offer such deals - making the legal validity of the offers unclear.

BBC: RELATED BBC SITES

The FBI took over the investigation earlier this month, after the justice department realised it would not be able to bring charges based on the guards' statements to the Bureau of Diplomatic Security, reported AP.

BBC: RELATED BBC SITES

The department's bureau of diplomatic security "has concluded that Ambassador Lawrence was a full-time student at Wilbur Wright College in Chicago from September 1944 to June 1945 and was not a Merchant Marine volunteer as he had previously claimed, " said James Foley, deputy spokesman.

CNN: AllPolitics - Lawrence Never A Merchant Marine