Police and Customs have seized $220,000 worth of methamphetamine and MDMA destined for Otago.
A 22-year-old Oamaru man was arrested after packages sourced via Facebook were posted to an Oamaru address related to him.
This week's seizure of 200g of methamphetamine comes after the same Oamaru man was arrested with 102g of methamphetamine - with a street value of $100,000 - last week.
He is facing charges of importing a class A drug and possession of a class A drug for supply.
In a separate seizure, a 21-year-old Dunedin man was arrested and is facing six charges related to a package containing 56g of MDMA, which equates to between 500 and 1000 tablets of ecstasy.
It had a street value of $20,000 and was also sourced via the internet.
Police intercepted the drugs before they arrived in Dunedin.
Southern district organised crime unit team leader Detective Senior Sergeant Malcolm Inglis, of Dunedin, said "it could have ended in disaster'' had the drugs made it to the streets.
"The amount going to Oamaru is a large seizure for that area,'' he said.
"It would make up a lot of individual sales.
"If that had got through, it would have flooded the market.''
The packages came from China and police and Customs were committed to disrupting the supply chain, Det Snr Sgt Inglis said.
"It's just sad to see these young people are now facing criminal charges for serious criminal offending,'' he said.
Customs profiling and intervention "expertise'' played a major role in the seizure, Det Snr Sgt Inglis said.
Customs investigations manager Maurice O'Brien said the interceptions were a "great outcome''.
Both men would appear in court at a later date.
