NEW YORK/PARIS (Reuters) - French authorities investigating corruption in international sports believe a Swiss partner of Japanese advertising giant Dentsu Inc played a "central and essential role" in deals used to embezzle sponsorship money and have asked Switzerland to raid its office and seize evidence, according to a person with knowledge of the probe and documents related to the case reviewed by Reuters.

French investigators have not accused Dentsu or its partner, Lucerne-based Athletics Management & Services, of wrongdoing. The companies work together on marketing and media rights for the International Association of Athletics Federations, the Monaco-based governing body for track and field. The IAAF's former president, Lamine Diack, and his son, Papa Massata, have been charged with embezzling from sponsorship and broadcast deals for those rights and other financial crimes in an inquiry that wrapped up in June and is set to go to trial.