Thieves targeted a building site - using large vehicles to steal heavy machinery.
The Persimmon Homes compound, Carleton Meadows, Penrith, was burgled overnight on Thursday into Friday.
The site, which is building family homes, had its storage containers forced open and heavy machinery stolen.
Offices on the site were ransacked and items removed.
A Cumbria police spokeswoman said: "The assailants used one or two large vehicles to take the heavy items away and travelled down The Parklands to Oak Road."
Police are appealing for witnesses who could have seen the vehicles leaving the area.
Officers are also looking for details of large vehicles which used the busy road overnight so their drivers can be traced and eliminated from enquiries.
The spokeswoman advised builders in the area to make sure they have adequate security on their sites.
Anyone with information should call police on 101.
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