Tokyo 2020 stars could face disciplinary action after police were alerted to a late-night drinking session at the Olympic Village, organisers have confirmed.
The Fuji News Network reported the incident occurred at around 2am on Saturday, with a number of overseas athletes said to be consuming alcohol and making noise on the streets of the complex.
Although alcohol is permitted in the Village, which houses Games competitors and team officials, it is only allowed to be drunk in athletes' rooms and without the company of others.
Toshiro Muto, CEO of the organising committee, said: "Multiple athletes and members of the delegation were at the park within the Village and they were drinking alcohol.
"We are aware of this fact. Currently we are investigating the situation and based on the result we are to take appropriate action.
"Regarding the details, we are not yet in a position and don't have sufficient information available at this moment.
"Regarding the police, after the incident occurred we have heard they came. However, in regards to their response we haven't learnt about the details at this moment."
No names of those involved have yet emerged, but it is the latest breach that Games chiefs have had to address.
Two Georgian judo athletes had their accreditation withdrawn after taking a sightseeing trip around Tokyo, defying the 'playbook' that instructs athletes they must remain within the Olympic bubble.
"The playbook violation regarding this incident is for the safety and security of the citizens and also for the safety of the athletes themselves, the adherence is very important," said Muto. "In most cases the rules are being followed; however, unfortunately there are cases of violation."
The Games was continuing on Sunday in the wake of another positive drugs test in athletics, with Kenyan sprinter Mark Odhiambo, who was due to compete in the 100 metres, found to have anabolic-androgenic steroids in his system and provisionally suspended. He has denied wrongdoing and the case has been referred to the Court of Arbitration for Sport.