Officers were alerted to suspicious packages at a rural address on Tuesday afternoon (June 11).
Following investigations, two men and three woman have been arrested at addresses across Shoreham, Brighton and Hove.
The men, aged 32 and 37, and two of the women, 28 and 29, were all arrested on suspicion of concerned in the supply of class A drugs. A 35-year-old woman was arrested on suspicion of the same offence and also the acquiring, use of possession of criminal property. All five remain in custody at this time and the investigation remains on-going.
Local policing commander Miles Ockwell said: “This is a significant policing operation with a large quantity of class A drugs taken off the streets.
“The investigation is on-going and enquiries will be continuing to establish the full circumstances surrounding the seized drugs.
“Anyone who notices any suspicious behaviour should always report it to us without delay.
“You can do this by reporting online or calling 101.”