Detectives have been granted more time to question three men - including one from Chesterfield - who were arrested on suspicion of terrorism offences on Tuesday.
This afternoon, a court approved an extension giving counter-terrorism police until January 1 to hold and question the suspects.
They are a 31-year-old from Chesterfield, a 22-year-old from Burngreave in Sheffield and a 36-year-old from Burngreave in Sheffield.
The men 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 Counter Terrorism Policing North East (CTPNE) said: “South Yorkshire Police and Derbyshire Constabulary continue to work closely with their partners and communities to reassure local people and protect the public.
“Searches continue at the address in Chesterfield at this time and the investigation is ongoing.”
A 41-year-old man from Meersbrook in Sheffield who was arrested has been released from custody without charge.
The CTPNE spokesman added: “We would like to reassure the public that public safety remains our priority at all times.
“Extensive enquiries have satisfied the investigation that there are no grounds to charge him with any offences.”
Superintendent Michelle Shooter, of Derbyshire Constabulary, added: “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.
“Please remember that, although speculation is natural, it is often wrong.
“We are continuing to support officers from CTPNE as the investigation continues.
“Our officers are patrolling the area to offer reassurance to the public.”
Armed police patrolling streets
The UK's terror threat level remains at 'severe', the second highest level.
Derbyshire police are urging people to continue to be vigilant but go about their business as usual.
As announced at the start of the month, armed police are patrolling the streets of Derbyshire over Christmas and New Yearm to make people feel safer.
If you see or hear something which could be terrorist related, act on your instincts and call the police in confidence on 0800 789 321.
In an emergency, always dial 999.
Visit act.campaign.gov.uk for more information.