Homes were evacuated after what police described as an 'anti-tank device' was found in a property.
Police and the Army bomb squad were called to Cotmanhay on Tuesday afternoon after the device was discovered inside a property in Thatchmarsh Close.
A Derbyshire Constabulary spokesperson later said that the device was made safe and was suspected to have been a replica.
There were concerns that it may have been a German Panzerfaust rocket launcher, designed as an anti-tank weapon and used during the latter stages of the Second World War.
According to police, a 100-metre cordon was set up around parts of Denby Hall Road, the roads connecting to it as well as parts of Skeavingtons Lane up to Bailey Brook Road.