Five men have also been arrested in two states.
Vacuum-sealed packets containing 350kg of the illegal tablets were found floating in plastic tubs in a shipping container, the Australian Federal Police (AFP) and Customs officials said in a joint statement today.
The container was x-rayed and unpacked at Port Melbourne on June 4, after it was sent from Canada via Hong Kong.
The container held 180 tubs of blue liquid dye, and Customs officials say 67 tubs contained the packets of ecstasy tablets.
The drugs were secretly switched with fakes and the load was monitored as it was delivered to an address in Clayton, in Melbourne’s south-east.
An operation involving 50 AFP agents then tracked the load as it was transferred to a residential address in Yagoona, in Sydney’s west.
AFP national manager (of) border and international network, Mike Phelan, said police conducted simultaneous raids on 11 properties across Melbourne this morning, resulting in two arrests.
There were nine raids in Sydney yesterday, resulting in another three men being arrested and charged with attempting to possess a commercial quantity of an imported border-controlled drug.
The maximum penalty for these offences is life imprisonment.
Mr Phelan said the sting had dismantled “an extremely sophisticated criminal syndicate … with strong international links”.
He said the two Melbourne men were still being interviewed but charges were expected today.
“This investigation is a significant victory in the fight to stop ambitious drug syndicates supplying Australia’s youth with a large amount of extremely harmful substances,” he said.
Customs has described the attempt to conceal the drugs as extremely unusual.
“We haven’t seen an attempt to import drugs in this fashion into Victoria before,” Customs Victorian director Jaclyne Fisher said.
“(But) Customs is alert to even the most outlandish concealment.”
The agencies said the seizure was believed to be the second largest in Victoria, and ranked amongst the largest in Australian history.