Several houses have been evacuated and nearby roads closed after a man was arrested on suspicion of explosives offences at a property in Belper, a town seven miles north of Derby, Derbyshire constabulary said.
Officers had attended an address in Acorn Drive at about 6pm on Friday. A man was then arrested after a search of the house uncovered a number of suspicious items, the force said.
Following advice from bomb disposal experts, a 100-metre cordon has now been put in place, requiring some properties in Acorn Drive and three other streets to be evacuated.
There is no indication as to how long the evacuation and road closures will be in place, police added.