Four men are facing drugs charges on Monday after the discovery of an importation syndicate selling GBL, also known as Fantasy.
Search warrants were executed in Wellington, Rotorua, Auckland and Canterbury.
The raids follow investigations by police and customs indicating more than 300 litres of the Class B controlled drug has been imported from China through the international mail system.
Detective Senior Sergeant Darrin Thompson says more than 20 importations of the drug have been identified with a street value of between $1.5 million and $3 million.
Mr Thompson says police and customs have been tracking the importations for 12 to 15 months.