Keen-nosed cops sniffed out almost 1,000 cannabis plants on their way to work.
The two officers from Essex police became suspicious after cycling past the building and decided to investigate further.
Officers used a disc cutter to force their way inside where they discovered hydroponics set-up to grow 991 plants.
Pc Lee Devall tweeted after the raid: “Team effort, the day shift have been clearing 911 cannabis plants from the warrant in #Chelmsford yesterday!”
Three men have been arrested on suspicion of the cultivation of cannabis and are currently being held in custody at Chelmsford Police Station.
The raid comes in the same month that more than 100 cannabis plants were seized during a crackdown on cannabis farms in Essex.
Officers raided one building in Lawford, Essex, after tip offs from members of the public.
Using an industrial disc cutter to enter, they seized 120 cannabis plants and a 65-year-old man from Clacton was arrested the following day.
They also raided a series of DIY factories in Tendering, Essex, after receiving intelligence from members of the public.