LONDON -- British police sent a bomb disposal team to a house in northern England Tuesday after officers carried out pre-dawn raids to arrest four men on suspicion of plotting terrorist attacks.

Counter-terrorism police detained the four men at their homes in Sheffield and Chesterfield in the early morning. Officers then cordoned off one of the houses and evacuated local residents as bomb experts arrived and searches were carried out.

The men, aged 22 to 41, were questioned at a police station. Police said the arrests were "intelligence-led and pre-planned" as part of an ongoing investigation.

The men have not been charged and were not identified.

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.