A Canadian-led drug syndicate has targeted Australia with nearly two tonnes of chemical imports sourced from India over the past two years.
A police investigation stopped the massive shipments of precursor drugs in Melbourne, preventing an estimated $300 million of ice or crystal meth from being made and trafficked.
Eight Canadians and two Australians have been charged as part of Operation Diamondback, including a 46-year-old man caught on Sunday as he checked in for a flight back to Canada.
A 27-year-old man and a 30-year-old woman were also arrested on Sunday at a Melbourne CBD apartment.
Victoria Police Assistant Commissioner Steve Fontana said all three Canadians are believed to have travelled to Australia to distribute drugs for the syndicate.
"This is a significant international syndicate that's been targeting Australia," he said on Monday.
"We're very pleased with the outcomes of the investigation."
The arrests came after police last month seized 650kg of pseudoephedrine hidden in vanilla powder jars.
Detectives secretly replaced the drugs, being kept in a self-storage unit in South Melbourne, with a non-harmful substance and watched the drug syndicate continue operations before pouncing on the trio.
The drug is used to make meth and ice but it is unclear if the Canadian gang was manufacturing the drugs or simply selling to locals.
In August last year, police revealed the taskforce had also seized 109kg of pseudoephedrine and three Canadians had been charged with drug offences during those raids.
Police said on Monday the taskforce, involving Victoria Police, Australian Federal Police, Customs and Border Protection and the Australian Crime Commission, had now wrapped up with a total haul of 1.9 tonnes of pseudoephedrine and 10 arrests.
Mr Fontana said it's not known why Australia was targeted, but suggested it was because it's a wealthy country with a booming drug market.
"We've got a lot of people here who think it's okay to use illicit drugs. We've really got to turn that culture around," he said.
The three Canadians arrested on Sunday - Catherine Marie McNaughton, 30, Edmond Proko, 46, and James Wray Kelsey, 27 - appeared briefly in court on Monday each charged with trafficking a commercial quantity of a drug of dependence.They will face Melbourne Magistrates Court again in January.