Four foreigners working at the Tokyo Olympics have been arrested on suspicion of drug offences after what local media reported was an evening out in the nightclub district of Roppongi.

The arrests shattered an unspoken compact that Tokyo would assume the huge risks of hosting an international event during a pandemic and in return, the tens of thousands of visiting athletes, officials, media and support staff would follow Japan’s rules.

The incident will revive opposition to the games and heap greater pressure on the Japanese government to crack down after multiple reports of foreigners out drinking in Tokyo without wearing masks.

Police said the men, who were working as electricians for British company Aggreko, were tested and found to have taken cocaine. Aggreko is among the 81 corporate sponsors and supporters of an event that has cost an estimated $25bn to host and raised more than $3bn in sponsorship.

NHK, Japan’s state broadcaster, reported that police had tested the four for drugs after they allegedly made a drunken attempt to enter an apartment building near the well-known bar district.

Despite government attempts to limit opening hours, bar and karaoke operators in Roppongi said many had remained open since February.

Police named the men as Ray Dalton, 22, and Gustavo Mosqueda, 24, both from the US, and British citizens John Lockwood, 46 and Anthony Kirk, 32.

In an indication of Japan’s fears that the Olympics could become a global superspreader event, organisers decided last week that the whole two-week showcase would proceed without spectators.

The Olympic Village, which officially opened on Tuesday, has been recast as a “bubble” to isolate athletes from the general public and the triumphant final stages of the torch relay through Tokyo will no longer take place on public roads.

Even after slashing the number of attendees, Tokyo still expects 41,000 coaches, officials, media and other staff to travel from abroad, including about 5,800 contractors.

The arrests of the four men over the incident in early July came to light just 10 days ahead of the opening ceremony of an Olympics that was initially postponed because of the Covid-19 crisis. It is proceeding despite warnings from Japan’s top epidemiologist.

Aggreko said it was assisting the police in their investigation and had suspended the four men. The company provides temporary generators for big events.

“Aggreko sincerely apologises for the concern this has caused the public . . . the athletes and the many thousands of people dedicated to the safe and successful running of the Olympic and Paralympic Games,” it added.

On Tuesday, Tokyo 2020 said: “Should the allegations turn out to be true, Tokyo 2020 will issue a strict warning to the company and advise them to take all possible measures to ensure that such an incident does not happen again.”