Cannabis plants with a street value of up to £50,000 have been discovered at a house in Essex.
Officers carried out a warrant under the Misuse of Drugs Act in Hereford Walk, Pitsea, at 1030 BST.
The entire building was being used to grow the plants, police said. Nobody was on the premises and no arrests have been made.
Inquiries are ongoing and police urged landlords to be aware of the warning signs that cannabis is being grown.
This includes intense activity when moving in, but very little afterwards and curtains or blinds being permanently drawn.
There may be a reluctance for landlords or agents to check the property, although the house may receive visitors at all times of the day.