A police cordon is in place and a number of streets are sealed off in a Sheffield suburb this morning.
The activity centres around the Wensley Street area of Fir Vale, but no details have yet been released by South Yorkshire Police.
A passer-by said a shop and a number of houses are within the cordon.
"If you drive down Hinde House Crescent the shop is at the bottom on the left and it's a built up housing estate that has lots of pathways between. They are cordoned off from the Hinde House Crescent side and then the police are parked up on the road at the bottom," she said.
"I know someone who had to go to the area for work purposes and police officers took footprints and they said a tent was up."