London police lost a set of keys at an Olympic venue last week but security was not compromised by the incident, officials said.
Officers securing Wembley Stadium, an Olympic soccer venue in west London, reported on Tuesday that a set of internal keys used on searches at the venue were missing, Scotland Yard said.
The force said that detectives failed to find the keys, but found no evidence of criminal offenses, suggesting that police probably misplaced the keys.
"There is absolutely no security concern in relation to the stadium as measures were taken immediately to secure all key areas of the venue," police said in a statement.
Organisers of the London Olympics stressed that relevant locks have been changed and there was no security breach.
Police declined to provide more details about what the keys were for.
Wembley is one of six stadiums hosting the men's and women's soccer tournaments during the games. The first soccer events began on Wednesday, ahead of the opening ceremony.
The key incident appeared harmless, but it was embarrassing for officials who are already on edge defending security arrangements for the London Games.
Just days before the games opened on Friday, Britain's government had to deploy thousands more servicemen to protect Olympic venues after private security contractor G4S admitted it could not hire enough security guards for the event.
Some of the servicemen called in on short notice have seen their leaves cancelled, while others have only recently returned from tours in Afghanistan.
The chief executive of G4S, Nick Buckles, apologised and said the fiasco was a national embarrassment.