A 55-year-old man has been arrested on suspicion of possessing explosives following concerns that prompted the evacuation of around 50 homes.
South Yorkshire Police said the evacuation was taking place at Chestnut Grove, Mexborough, near Doncaster.
A spokeswoman said: "Residents are currently being evacuated from Chestnut Grove in Mexborough, and the surrounding area, following the discovery of potentially hazardous material at a property.
"A cordon has been put in place while the material is assessed, to ensure the safety of the public.
"Officers from South Yorkshire Police and partner agencies, including South Yorkshire Fire and Rescue Service, are currently at the scene.
"South Yorkshire Police would like to thank members of the public for their patience and co-operation while inquiries continue."
The spokeswoman confirmed a 55-year-old man had been arrested.