More than 500 cannabis plants with a street value of up to £200,000 have been found in a bungalow.
The plants could sell for between £100,000 and £200,000 a year
The cannabis factory was uncovered by officers from Thames Valley Police at the rented property in Winnersh, near Reading, Berkshire, on Thursday.
Three rooms and the loft had been converted for growing the cannabis and dead plants were found in a shed.
With three or four annual yields, the plants would have made between £100,000 and £200,000 a year, police said.
No-one was in the property at the time of the raid and no arrests were made.