He said Aon's internal investigation is proceeding "expeditiously" and there was no "particular time table" for completion of the probe. The firm, he said, is most interested in making a "thorough and proper" investigation before taking action.

Mr. Sullivan said the firm did not have plans to announce publicly any disciplinary action that may be taken against employees in relation to the probe.

Yesterday, Aon Chairman and Chief Executive Officer Patrick G. Ryan said that employees at Aon, for the most part, have acted appropriately in placing insurance contracts for clients in accordance with the company's code of conduct and the firm's values. However, Aon has found "indications that some employees have not always followed these principals."

The investigation is centered around abuse of the contingency commission fee system.

In mid-October, New York Attorney General Eliot Spitzer announced a suit against Marsh & McLennan Companies, the parent company of insurance broker Marsh, alleging bid-rigging, steering of insurance contracts and other contingent fee abuses related to volume placements.

Subsequently, the world's three major brokers?Marsh, Aon, and Willis?said they would discontinue the practice of accepting contingency fees.

The probe has reportedly led to the firing of at least five employees at Marsh who were allegedly part of the scandal. Marsh has declined to name the employees.