US Weapons Inspector Charles A Duelfer also said that companies in several countries, including India, may have sold Iraq dual purpose equipment.
The Volcker panel had named Natwar Singh, who was divested of External Affairs Ministry, and the Congress party among the non-contractual beneficiaries of the oil-for-food programme in Iraq.
Justice R S Pathak was probing allegations against Congress and Natwar Singh in the oil-for-food scam.
Annan was cleared of involvement in the United Nations Oil-For-Food programme in Iraq.
Former Federal Reserve chairman Volcker's report alleged that 1.8 billion dollars in bribes and illegal surcharges were paid to the regime of former Iraqi president Saddam Hussein.
Half the 4,500 companies that took part in the United Nations oil-for-food programme in Iraq allegedly paid kickbacks or illegal surcharges and are being given a chance to respond to the charges, two top investigators said.
Former union minister Natwar SinghNatwar Singh on Saturday hit back at the Congress saying the party has conveniently forgotten that it too was named in the Volcker report as a "non-contractual beneficiary".