Tokyo Olympic organisers are investigating the fraudulent purchase of 6,900 tickets worth 180 million yen (£1.36m) that were obtained in an online lottery for Japan residents.
Ticket interest in next year's showcase event is unprecedented with demand at least 10 times above supply.
Earlier this year Japan passed a law that prohibits ticket scalping, with a 1 million yen (£7,396) fine and one-year jail term or both.
However, the law has loopholes and does not apply to tickets distributed for free or given away as gifts, or tickets without a purchaser's name.
This applies to many tickets coming from the International Olympic Committee, the 206 national Olympic committees, or major sponsors.
Organisers were in the process of voiding the tickets which were bought using fraudulent IDs.
"We are consulting with the police on this matter, and if there are other cases where unauthorised purchases are suspected, we will deal with those as needed," Tokyo organisers have said.
- Olympics 2020: Is Tokyo ready?
- ITF announces changes for Tokyo 2020
- Russia facing possible Olympics ban
In a separate matter, organisers have announced the results of their latest ticket lottery for Japan residents.
The outcome is much like the first lottery in May with tickets very tough to get, and many in Japan will be left out.
Organisers say 1.4m people applied in the August phase, and only 120,000 were successful landing 350,000 tickets.
Tokyo organisers say they have now sold 3.57m tickets to Japan residents in both lotteries with the Japanese general public expected to get between 70 and 80 per cent of the estimated 7.8m tickets listed as available.
The rest are for sale outside Japan through Authorised Ticket Resellers the Olympic agents contracted to sell tickets outside Japan or go to sponsors, national Olympic committees, sports federations, and dignitaries.
Organisers are planning another lottery this fall for Japan residents but have declined to say how many tickets will be available.
Tokyo is a reversal from recent Olympics in Rio de Janeiro and Pyeongchang, South Korea, when tickets were unsold and many events were poorly attended. That won't be the case with 35m people in Greater Tokyo looking to attend.