Searches have been stood down at properties raided by anti-terror police in Sheffield and will resume in the morning.
A spokesperson for the North East Counter Terrorism Policing Unit, which is leading the counter-terrorism operation, said: "All searches have now been stood down for the evening. Searches at the scenes in Burngreave and Chesterfield will resume in the morning.
"The remaining scenes have now closed. The four men remain in custody at this time."
Earlier this evening the Royal Logistics Bomb Disposal Team arrived at about 5pm outside the Fatima Community Centre in Brunswick Road, Burngreave, which has been cordoned off by police.
The squad are understood to have earlier carried out a controlled explosion during a counter terrorism raid in Chesterfield.
The North East Counter Terrorism Policing Unit has raided four properties in Sheffield today - two in Burngreave, one in Stocksbridge and one in Meersbrook. A search warrant was also executed at a property in Chesterfield.
Three men, aged 22, 36 and 41, arrested in Sheffield and a 31-year-old man arrested in Chesterfield were taken to a police station in West Yorkshire for questioning.
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.
A spokesman for the North East Counter Terrorism Policing Unit said the raids were 'intelligence led' and 'pre-planned'.