Masked men allegedly forced a lorry driver to open the back of his vehicle before stealing goods which they carried away in a large bag.
The robbery happened at 5.30am on High Street in Ruskington on November 12 after a lorry had parked up to deliver goods to a local shop.
Two men wearing head coverings are then reported to have made the driver open the rear of the lorry before getting away with the goods.
The offenders are suspected to have had a vehicle parked nearby, police said.
Police are appealing for witnesses and anyone in the area at that time, in a car or on foot, should contact them on 101 or via email at [email protected] quoting incident number 35 of November 12.
It can also be reported anonymously through Crimestoppers on 0800 555 111.