Businesses that won contracts related to the test events for the Tokyo Olympic and Paralympic Games are reportedly suspected of having rigged bids.

Tokyo prosecutors are believed to be looking into the suspected violations of the anti-monopoly law in cooperation with the Japan Fair Trade Commission.

Sources say advertising agencies and other firms are suspected of adjusting who would win the bids for the orders placed by the Games organizing committee.

The test events were carried out to check the security measures for each event site and how athletes would move around the venues.

The committee held 26 biddings in 2018 to select businesses that would be entrusted with the planning for the test events.

Nine companies and one consortium won tenders worth more than 500 million yen, or some 3.6 million dollars at the current exchange rate. The successful bidders included Japan's largest ad agency Dentsu.

The sources say the suspected collusion surfaced during the investigations into a series of bribery cases involving Takahashi Haruyuki, a former executive of the Games organizing committee.

Takahashi, a former Dentsu executive, has been indicted four times on charges of receiving nearly 200 million yen in bribes from five firms, including Games sponsors. He is accused of giving them favorable treatment for businesses related to the Games.

Dentsu told NHK that it is trying to confirm the facts.