Police said an evacuation of a residential area in Derbyshire is "purely a precaution" after a potentially volatile substance was found in a flat.
A 55-year-old man has been arrested.
Superintendent Paul Markham, who is in charge of the operation, said:
We are not looking for anyone else in connection with this matter and we are hoping that people will not be inconvenienced for too long.
The evacuation is purely a precaution to ensure everybody's safety and residents will be allowed back home as soon as possible.