Cannabis plants worth around £1.5m have been discovered in a Hucknall building.
The haul is believed to be one of the largest ever in Nottinghamshire.
Police made the discovery after carrying out a search warrant at Alexandra House in Watnall Road, Hucknall, earlier this morning.
It is thought there are in excess of 3,000 plants inside, which have an estimated street value of around £1.5 million.
Two men have been arrested and will be interviewed today.
Ashfield South Inspector Nick Butler said: "Police discovered a sophisticated set-up inside with thousands of plants and hydraulic systems.
"Officers will remain at the scene today while the plants are recovered and it could take us days to dismantle everything.
"Police will act on any information about local criminality and I urge anyone with information about crime happening where they live to get in touch."
Contact Nottinghamshire Police on 101 or call Crimestoppers anonymously on 0800 555 111.
