Police are investigating after around 900 hundred cannabis plants were discovered near Coalville.
Officers were called to an industrial unit in Walker Road, Bardon Hill after the owner of the building reported he could not gain access.
When officers forced entry, they found hundreds of cannabis plants being grown in several different rooms.
No-one was present at the unit and no arrests have been made but police remain in the area.
Sergeant Ryan Ludlam said: “Our enquiries into the discovery of these plants is continuing today, and officers remain in the area while they are recovered.
“We think there are around 900 plants. The set up inside the unit was sophisticated. Tackling the production of drugs is one of our key priorities and we would like to speak to anyone who has information regarding this grow.
Police say they are keen to speak to anyone who visits or uses the industrial units in Walker Road, and who may have seen someone – or a group of people – "acting in a manner that aroused suspicion".