LONDON (AP) – British police have arrested a fifth man suspected in plotting an extremist attack.

A police spokesman said Saturday a 21-year-old man was arrested late Friday on suspicion of preparing “acts of terrorism.” The man was not identified or charged.

Two buildings are being searched in the city of Sheffield, 170 miles (275 kilometers) north of London, following the arrest, police said Saturday.

Four other men were arrested in the Sheffield area on Dec. 19. Two of them have been charged with engaging in the preparation of an act of terrorism.

The two men are both Kurdish Iraqis. They are set to appear in court in January.

Police say one of the men arrested Dec. 19 has been freed while the other remains in custody.