Officers have been granted until Christmas Day to decide whether to charge four men held as part of an operation to foil a suspected Christmas atrocity.
Chip shop owner Andy Sami Star, 31, as well as three other men, aged 22, 36 and 41, are being questioned by police after raids on Tuesday morning.
Specialist teams returned to the scene in Chesterfield, Derbyshire on Wednesday to assist with ongoing searches, North East Counter Terrorism Unit said.
Warrants of further detention have been granted following the terrorism-related arrests in #Chesterfield and South Yorkshire, to allow further time for questioning the four men in custody https://t.co/0H4ihSySHP— Derbyshire Police (@DerbysPolice) December 20, 2017
The force have asked residents to be “alert but not alarmed” after the raid on Mermaid Tradition Fish Bar on Sheffield Road.
In Sheffield, a mosque and community centre in Brunswick Road, Burngreave, was sealed off, with local people telling stories of being woken at 6am by a series of loud bangs and camouflaged officers with guns.
According to witnesses a man was later taken from the property.
An Army bomb squad was deployed in Chesterfield, where armed officers and investigators focused on the fish and chip shop.
A close friend of Star, from the Kurdish community, who did not want to be named, said: “I can’t believe it to be honest. I knew him, he was my friend.
“I don’t know what happened, he was a nice guy. All I can think is that someone has taken advantage of him. I am sure he is innocent.
“I don’t know the three other guys involved, but they must have used him, taken advantage. I was so shocked when I was told he had been arrested.
“It is very sad. I can’t say anymore than that.”
Superintendent Michelle Shooter of Derbyshire Police said: “I would like to thank the people of Chesterfield for their patience and understanding during the unavoidable disruption.
“We’d ask that people are calm, resilient and measured in what they say and how they act during what is a difficult and concerning time for local communities.
“We are continuing to support officers from Counter Terrorism Policing North East as the investigation continues.
“Our officers are patrolling the area to offer reassurance to the public.”
South Yorkshire Police Assistant Chief Constable David Hartley said: “I’d like to thank everyone for their support and patience over the last 24 hours, which has understandably caused some concern within our communities
“We are continuing to support the investigation and as planned throughout the festive period you will see an increased visibility of both unarmed and armed patrols right across the county.”