Detective Senior Sergeant Tim Leitch said the arrests had prevented the distribution of a large quantity of GBL, also known as fantasy or rinse, into the community.
"It is often dangerously used in combination with other drugs or alcohol and over doses have occurred in the past.
"GBL presents significant health risks to users," he said.
"The sole motivation for offending of this type is to make money with no regard to the harm it causes to our communities."
Customs manager investigations Mark Day said the department was always on the lookout for harmful drugs.
"It doesn't matter how people try to import drugs, whether it is through the mail, by freight or in person we make every effort to keep these harmful substances off our streets and away from our communities.
"It is a reminder to people who attempt to bring drugs across the border that we are watching and we will pursue you."
