Police are appealing for landlords in the Grantham area to check that properties rented out are not being used for criminal activity.
Officers were called to two incidents on December 22 and January 6, after tenants in rented properties on South Parade and Dysart Road were found to have been growing cannabis.
In both these incidents, the tenants payed their rent in full and immediately changed the locks.
A spokesperson for Lincolnshire Police said: “If you have rented out a property recently, and are suspicious that criminal activity could be taking place, please contact 101 or 999 in an emergency.
“If you believe suspicious activity is taking place in a property, please call 101 or 999 in an emergency.”