Scotland Yard said security for the London Olympics had not been compromised after police documents were reportedly found on a train.
According to the Sun, a senior officer left files on a train that detailed plans for policing this summer's Games.
But a Metropolitan Police spokesman insisted the documents were not thought to be “operationally sensitive”.
The dossier reportedly included minutes of meetings where anti-terrorism plans were discussed.
It was also said to contain details of pre-Olympics rehearsals, an explanation of emergency “lock-down” procedures and plans to avoid traffic congestion.
The files also contained the names and mobile numbers of police officers, the newspaper said.
A commuter reportedly found the documents on a train in Dartford, Kent, earlier this month and handed them to the Sun before they were later returned to police.
The Met spokesman said: “On Thursday, January 5 a Metropolitan Police Service officer lost his bag containing a number of documents.
“The officer reported the loss to a senior officer. Directorate of Professional Standards have been informed as is routine.
“We do not believe that the bag contained operationally-sensitive documents.
“The documents are now back in police possession.”