British police arrested on Tuesday four men on suspicion of plotting terrorist attacks. Police sent a bomb disposal team to a house in northern England after officers carried out pre-dawn raids to arrest the suspects. Three men, aged 22, 36 and 41, were held after raids at their homes in Sheffield and a 31-year-old was detained at an address in nearby Chesterfield. Officers then cordoned off one of the houses and evacuated local residents as bomb experts arrived and searches were carried out. “The arrests were intelligence-led and pre-planned as part of an ongoing investigation by Counter Terrorism Policing North East and (domestic security agency) MI5,” West Yorkshire Police said in a statement. They added: “The public may have heard loud bangs at the time police entered the properties. We would like to reassure them that this was part of the method of entry to gain access.” The men have not been charged and were not identified. There were no details about what the men were suspected of planning. They are being questioned on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism. The official terrorist threat level for Britain is "severe," indicating an attack is considered highly likely. Britain saw five attacks in London and Manchester this year, and Home Secretary Amber Rudd said earlier this month that authorities have foiled nine terror plots since March.