Police have received several reports of diesel being stolen from machinery at premises on Station Approach, Horsted Keynes.
More than 1,000 litres of diesel has been stolen so far along with the damage to the fuel caps to gain entry.
Sussex Police say contact them on 101 or Crimestopper 0800 555 111 if you can help, quoting serial number 0335 of 10/01/14.
Elsewhere, a garage on Freshfield Lane, Danehill had its lock drilled out and several items removed.
The items were left outside the garage so it is believed the offenders were disturbed.
Entry was gained via a neighbour’s field where the chain on the gate was broken off. (Serial 0319 of 17/01/14)