Two men were arrested after police uncovered a cannabis factory in Shantallow on Tuesday.
The men, aged 24 and 47, were arrested on suspicion of cultivating and possessing cannabis with intent to supply.
Chief Inspector Tony Callaghan, said the search was part of a series of operations carried out by local police and Tactical Support Group colleagues.
A total of 20 mature cannabis plants were uncovered. The men remain in custody at Strand Road police station.
Meanwhile, in another search in the Shantallow area on Tuesday, scales, a grinder and a bag containing suspected cannabis were seized.
A man aged 27 and a woman aged 28 were arrested on suspicion of possessing Class B drugs; possession with intent to supply and being concerned in the supply of a Class B drug. They were later released pending further enquiries.
In a third search in the area no items were seized, however the offence of abstracting electricity was identified.
Chief Inspector Callaghan added: “Tackling the issue of illegal drugs is a priority for us. We receive vital information from people in the community and I would like to thank them for their continuing support.”