A man has been arrested on suspicion of making an explosive substance for unlawful purposes.
Police said "following the execution of a warrant" in Brooklyn Road, Cheltenham, they arrested a 57-year-old man in a "pre-planned operation".
Sgt Simon Ellson, from Gloucestershire Police, said: "There are no concerns regarding any terrorist activity."
Three properties on Brooklyn Road have also been evacuated and officers are asking people to avoid the area.
The force said it was "working with other blue light services to ensure everyone's safety".
A spokesman said searches at the property would continue on Friday.
Assistant chief constable Julian Moss said it was "important to address" concerns raised on social media by local residents.
"We are aware of questions being raised regarding previous activity at an address in Brooklyn Road," he said.
"The public have raised valid concerns and we are fully informed of everything that has taken place previously in the area and are working with all agencies involved to understand the facts that have led us to the latest events.
"We will release more information as and when it is appropriate."