Three masked men have attempted to rob Hemswell Antiques Centre, near Gainsborough, in Lincolnshire.
Several female staff were opening up the centre at 9.45am on Wednesday when they were approached by three men who had been waiting inside.
The women fought off the intruders who then fled via a window.
It is believed they left the scene in a blue 4x4 vehicle travelling across the field at the back of the unit.
The men are believed to be white, all wearing dark clothing and wore Halloween-type masks.
The investigating officers are appealing for anyone who may have seen any suspicious activity in the area during the previous evening.
Anyone who thinks they can help should contact Detective Constable Tina Kennedy of Gainsborough CID via the non-emergency 101 number, quoting incident number 111, or Crimestoppers anonymously on 0800 555111