Two men wearing balaclavas a convenience store near Sudbury earlier this week.
The incident happened between 9.20pm and 9.45pm at the East of England Co-op store in The Drift, Great Cornard, Suffolk police said.
During the incident, men allegedly ordered members of staff to open the safe, before forcing open the tills and stealing a quantity of cash.
The shop workers were left shaken but were otherwise unharmed.
Both robbers were wearing black balaclavas, while one was carrying a crowbar, said the police.
The man who ordered the safe opened was described as white, about 5ft 9ins tall, with a stocky build. He spoke with a local accent.
The police have asked locals to report any suspicious behaviour in the area at the time of the incident to Suffolk police.