A man armed with a knife snatched cash from a till at Homebase in Luton on Tuesday (December 11).
The incident happened at the Enterprise Way store at 7.40pm, and employees chased the man from the store but lost sight of him.
The offender is described as a man with a mixed race appearance and slim build, 6ft tall and wearing a black hooded top and blue denim jeans.
DS Emma James said: “There were a number of people in the store at the time of this offence including a man who was standing at the customer services desk who has still not come forward to assist with this investigation. I urge anyone who was in the store or the area on Tuesday night or anyone who can help identify the man responsible for this crime to come forward and speak to officers.”
Anyone with information relating to this investigation can contact DS James, in confidence, on 01582 394445, or Bedfordshire Police on 101, or text information to 07786 200011.
Alternatively you can contact the independent charity Crimestoppers, anonymously, on 0800 555 111.