Three firearms, two grenades and an electric stun gun were among weapons uncovered during a police search in Londonderry.
Ammunition, a CS gas canister and drugs with an estimated street value of £20,000 were also found in the property at Hawkin Street.
A 28-year-old man arrested at Hawkin Street remained in custody.
In another search at a property in Queen's Court, a four-figure sum of cash was seized.
A 35-year-old man arrested in that area has been released on bail pending further police inquiries.
All the items seized are being forensically examined.
The search operation was conducted by detectives from the PSNI's Organised Crime Branch.