Detectives are appealing for witnesses following an attempted robbery at a shop in Brimington.
Police were called to Premier Express, on Station Road, just before 7pm last night after a man entered the store and threatened staff.
A scuffle ensued and a member of staff suffered a dislocated shoulder for which he received hospital treatment. The offender fled the scene before police arrived.
The offender was in possession of what police believe to be an imitation gun.
He is described as white, in his late 20s to early 30s, of slim build, with short dark hair and dressed in black clothing.
Extensive searches were carried out in the area and officers are making ongoing efforts to find the offender.
Officers are investigating a link between this incident and a shoplifting offence at Co-op in Brimington at about 6.30pm yesterday.
Detective Chief Inspector Julian Wilson said: “I want to reassure the public that incidents like this are extremely rare and we have extra officers in the area making every effort to find the person responsible.
“I would urge anyone who witnessed the incident or any suspicious behaviour in the area to contact police immediately.”
Anyone with information is asked to call Derbyshire police on 101 or Crimestoppers anonymously on 0800 555 111.