Thieves have stolen about 50 silage bales from farmland in Clackmannanshire.
The bales of grass - used for animal feed - were taken from a field near the Meadowhill open cast mine in Forestmill.
Police said heavy-duty farm machinery would be needed to lift the bales, which can weigh up to one tonne each.
Local farmers have been warned to be vigilant and report anything suspicious to police.
The theft of the bales, which were covered in black plastic, took place over the weekend of 28-31 January. They are worth about £1,000 in total.
Drivers who passed the area at that time and who saw the silage bales being removed are being urged to contact police.
Pc Simon Brown said a forklift truck or tractor would have been needed to transfer the bales to a trailer.
He added: "It's an unusual theft, but because of the poor harvest last summer these bales are becoming quite scarce - so we could see more in the future."