The army bomb squad has carried out a controlled exposion in Chesterfield.
The news comes after four men - a 31-year-old from Chesterfield and three others from Sheffield - were arrested on suspicion of terrorism offences on Tuesday morning. They are currently being questioned by detectives.
Since Tuesday, the Mermaid Traditional Fish Bar on Sheffield Road has been cordoned off by police.
In a statement issued this afternoon, a spokesman for Counter Terrorism Policing North East said: "As part of the ongoing investigation and search of the premises in Chesterfield, the army bomb disposal unit attended and has carried out a controlled explosion at a nearby safe location.
"The controlled explosion took place to safely dispose of material found at the property.
"A cordon remains in place around the premises.
"No premises have been evacuated as a result of this activity."
Superintendent Michelle Shooter, of Derbyshire Constabulary, added: "I would like to thank the local residents and businesses for their continued patience and understanding while the detailed search of the premises continues.
"Public safety is our priority and we understand events like this can be concerning.
"Our message remains for local people to remain alert but not alarmed."