The organizing committee of next year's Tokyo Olympics says nearly 7,000 tickets may have been sold to applicants who used fake personal data to take part in the lottery.
The committee said on Friday that about 30,000 of the registered IDs for ticket purchases were obtained using false personal information.
It said the IDs were used to access the first round of the lottery in May, and tickets worth about 1.7 million dollars were purchased.
The committee said it took steps to block purchases from being made with suspicious IDs during the second round and the lottery for Paralympic tickets.
There were 5.12 million entries for the first online lottery, and 4.16 million applicants missed the chance to get tickets. The organizing committee decided to hold a second round only for those who came away empty-handed.
The committee is considering making purchases made with improper IDs invalid.
An official of the marketing division, Hidenori Suzuki, says the committee will continue monitoring illicit ticket purchases.
Suzuki says tickets obtained with improper IDs may be sold on the Internet, and he urges people never to buy them.