Masked raiders armed with a lump hammer stole cash and cigarettes from a store before locking staff in a toilet and fleeing.
The robbers struck just moments after staff had arrived at Spar in Wombourne to prepare to open for the day.
Three workers arrived at the front entrance of the Windmill Bank store at 7.30am to get ready for the day’s business.
But when they went to the rear of the building to collect deliveries, two men dressed in black and wearing masks and gloves forced their way into the shop.
A third man later joined them. One of the men was carrying a small lump hammer.
They grabbed cash and cigarettes before locking the workers – two men and one woman – in the toilets. The robbers then fled in a car believed to be an orange Focus.
None of the workers were injured in the raid but one was taken to Russells Hall Hospital in Dudley suffering from shock.
Det Con Colin Roberts, from Cannock CID, said: “We have had a sighting of the car at around 6.40am in Wombourne.”
Anyone with information is asked to call Staffordshire Police on 101.