Raiders forced their way into construction sites in Alfreton and Langley Mill in two separate break-ins overnight between Tuesday, February 11 and the following morning.
A mini-digger, trailer and tools were taken from a site at Amber drive, Langley Mill.
The digger was stripped of valuable items inside and dumped on Chapel Street in Ilkeston. The trailer and tools have not been recovered.
During the same night a Honda generator, angle grinder and power tools were taken from a building site at Watchorn Lane, Alfreton.
Locked storage cabins were broken into.
If you have any information call police on 101