Army bomb disposal experts have started examining a large number of mortar shells found at a building site.
Staffordshire Police said the operation at the site of a former munition factory in Chasetown, near Burntwood, was ongoing and was likely to continue on Friday.
A force spokesman said: "No further excavations will take place, but a 100m cordon remains in place as a precaution for public safety.
"Any live shells will be detonated safely under controlled conditions.
"The A5190 will close when any devices are detonated on site, while other devices will be taken to a second side for safe detonations."
Staffordshire Police tweeted a picture earlier on Thursday showing dozens of rusting shell casings after it was called to the scene, which is being redeveloped for housing, at about 8.20am on Thursday.