Counter-terror police have concluded their search at one of the properties raided in Sheffield this morning.
A spokesperson for the North East Counter Terrorism Policing Unit said specialist officers have finished their work at a property in Stocksbridge.
They added that the other four searches at two properties in Burngreave, Meersbrook and another in Chesterfield are ongoing.
Three men, aged 22, 36 and 41, arrested in Sheffield and a 31-year-old man arrested in Chesterfield remain in custody.
All four were arrested on suspicion of being concerned in the commission, preparation or instigation of acts of terrorism under section 41 of the Terrorism Act 2000.
They have been taken to West Yorkshire for questioning.
A spokesman for the North East Counter Terrorism Policing Unit, which led the operation, said the raids were 'intelligence led' and 'pre-planned'.
The Royal Logistics Bomb Disposal Team are understood to have carried out a controlled explosion during the raid in Chesterfield.