Thieves broke into a post box in Castle Bytham.
Police are appealing for witnesses after the post box on the outside of a farm premises in Castle Bytham was forced open, between 8am and 12.30pm on November 27.
Police said it is believed that the offender made at least two visits to the post box during that morning to try and retrieve letters from it.
A black BMW was seen in the area at the time, and the driver of this vehicle was seen to go to the box.
Anyone who saw any suspicious activity in the area that morning, or who saw the black BMW in the vicinity, should call police on 101 quoting incident 239 of November 27.