The residents of more than 100 homes have been told it is highly unlikely they will be able to return tonight after being evacuated following a police operation over the misuse of explosives.
Two men were arrested during the operation in Cheltenham, Gloucestershire, and remain in custody.
Officers initially searched a home in Brooklyn Road in the Hester's Way area where they arrested a 52-year-old local man under the Explosives Substances Act, police said.
Police then found items "requiring further investigation" in a garage in Buttermere Close in the Up Hatherley area of Cheltenham.
A 31-year-old man was arrested and an explosive ordnance disposal team was called to search the building.
A 100-metre cordon was put in place around Buttermere Close, which was later extended to 200 metres.
Explosives teams have been at the address in Up Hatherley and the address in Hester's Way throughout the day, police said.
Assistant Chief Constable Richard Berry, of Gloucestershire Police, said: "We sincerely apologise to all of those affected by today's events.
"We know these are difficult circumstances but we ask for their patience and support.
"This is a painstaking and methodical process in which everyone's safety is absolutely paramount.
"For this reason the specialist searches that are being carried out cannot be rushed.
"Unfortunately this means that we are now almost certain we won't be able to clear the cordon this evening to allow people back into their homes."
A police spokesman added: "Two men, a 52-year-old and a 31-year-old have been arrested under the Explosives Substances Act 1883 in connection with the operation. They currently remain in police custody."
Residents have been taken to two local community centres, St Margaret's Hall on Coniston Road and Hillview Community Centre, and are being asked to think of any vulnerable residents in the area who may need additional support.
Any residents affected by this incident can ring 0800 092 0410 to be directed to further information.