An inquiry is under way after files containing security details about the Pakistani president's visit to London were found by a member of the public.
Gen Pervez Musharraf arrived in Britain on Sunday
The files are believed to contain detailed security arrangements for Gen Pervez Musharraf's visit this week, including police codes.
Scotland Yard said the policing operation had been reviewed.
A spokesman said President Musharraf's safety had not been compromised, as the papers had been handed in promptly.
"We cannot discuss who was responsible for the documents, only that they contained the policing arrangements for the official visit," said the spokesman.
The papers are believed to have been found by a member of the public in a street in Mayfair and given to the Mirror newspaper.
The police spokesman said the newspaper handed the report over on Monday.
The force's Directorate of Professional Standards is investigating the circumstances surrounding the loss of the documents, he said.
Gen Musharraf held talks with Tony Blair on Monday.
He arrived in Britain on Sunday night after flying from the United States, where he met President George W Bush.
He is due to visit the Pakistani community in Manchester on Tuesday afternoon.