Police erected a 100-metre cordon around a house in Somerset on Friday after arresting a man under the Explosives Act.
Avon and Somerset Police said the 36-year-old man had been detained after police executed a warrant on the house in Burnham-on-Sea at 7.45 a.m.
They declined to give further details about the nature of the incident or what had prompted it, but said the cordon had been set up as a precaution.
Evacuation of nearby properties was also being considered.
We will be doing everything we can to minimise disruption to people's daily lives, but public safety must be our top priority, a statement said.
(Reporting by Michael Holden)