A huge amount of cocaine's been stopped from entering Christchurch - worth nine million dollars

Customs seized more than 25 kilograms of the Class A drug at Lyttelton Port in March.

It prompted a nation-wide six-week investigation and the arrests of four men in Christchurch, Wellington, Tauranga and Auckland.

Police say this seizure equates to more than 250-thousand doses of cocaine.

They say crime groups are using every method possible to exploit any vulnerabilities within supply chains.