Belgian police have also begun an inquiry into the affairs of Mr Emerson, a former EU ambassador to Moscow, and sources said the FBI was being kept informed.
In one of the biggest ever EU corruption inquiries, investigators are following leads in Russia, Belgium, Canada, the US, Jersey and Cyprus.
The European Commission, has stressed that Mr Emerson is "innocent until proven guilty".
The documents received by the commission's fraud unit, the UCLAF, and also passed to the Independent on Sunday, contain transcripts of private letters, sent by electronic mail, allegedly from Mr Emerson to business contacts in Russia. They suggest that Mr Emerson may have set up a consultancy company to pursue private business interests while posted to Moscow.
One letter, allegedly written by Mr Emerson, discusses a financial deal with a St Petersburg businessman, Ilye Baskin. The letter refers to "our consultancy company" and to a complex "project", apparently with connections in Kirghizia.
Also being examined by the authorities is a letter allegedly written by Mr Emerson to a "tax expert" in the Moscow office of Coopers and Lybrand, the accountancy firm. This also refers to "our consultancy company" and outlines arrangements for sending payments to offshore accounts in Jersey and Cyprus.
The documents also include letters to the same business contacts allegedly written on the same computer by a Russian woman, Elena Prokhorova, who was employed at the EU Moscow embassy while Mr Emerson was ambassador.Reuse content