Manawatu Police and NZ Customs have shut down a large scale drug operation.

Five people have been arrested and will face drug charges after the two day operation this week.

2.5kgs of what is thought to be synthetic cannabis was seized by customs, as well as 16 pounds of plant material.

Detective Sergeant Dave Thompson says detecting the powder before it was sold has prevented harm being inflicted on the local community.

All five people arrested and charged during the sting will appear in the Palmerston North District Court in the coming weeks.