Six men arrested by counter-terrorism police investigating a plot to attack the Pope were released without charge.
The men, all believed to be of North African origin, were arrested on Friday in London.
A Metropolitan Police spokesman said: "Six men who were arrested under the Terrorism Act 2000... were all released without charge late on Saturday night and early this morning."
Police searched eight homes in north and east London and two business premises in central London, including a street cleaning depot as part of the investigation.
The Met said the searches of the premises had been completed and had not revealed any weapons or suspicious materials.
Newspapers reported that the men had simply been overheard sharing a joke in their canteen. The BBC quoted Scotland Yard sources saying that the men posed no credible threat.
The six are aged between 26 and 50. One of the men, a 29-year-old, was arrested at a home in north London shortly before 2pm on Friday.
The five other men, believed to be street cleaners, were arrested at gunpoint as armed officers swooped on their base as they prepared to start their shift shortly before 6am on Friday.
They work for Veolia Environmental Services, a contractor which employs 650 on-street staff to keep the streets of Westminster clean.
The cost of policing the Pope's visit will exceed £1.5m and is being co-ordinated by South Yorkshire Chief Constable Meredydd Hughes.