A biosecurity officer checking a shipment of basmati rice for pests has helped foil an international drug syndicate.
A Melbourne agriculture department officer inspected a shipment of rice arriving from India in July and noticed the powder in the bags wasn't the normal rice residue.
It turned out to be 274kg of ephedrine scattered throughout the 3600 bags of rice.
The third biggest seizure of ephedrine in Australia, it could have been turned into 200kg of crystal methamphetamine with a street value of up to $200 million.
The discovery led to the arrest of two Canadians and an Australian in Sydney and Melbourne this week.
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An Indian man has also been arrested in India, allegedly responsible for organising the drugs and sending the shipment to Australia.
Investigations are continuing and police expect more arrests to be made.
Commander Ian McCartney, the AFP's national manager of crime operations, said the seizure was a great result for law enforcement in Australia.
"This is a sophisticated organised crime syndicate," he told reporters in Canberra on Wednesday.
The operation showed the success of Australian agencies working together, as well as with their international counterparts, he said.
The operation began on July 16 with the arrival of the shipment of bags labelled "basmati rice".
"The officer who did the inspection was really on the ball," agriculture department assistant secretary Tim Chapman said.
"He realised that the powder that was in the bags of rice that were tested wasn't just residue from the rice, there was something different about it."
The powder was referred to customs for further testing, which confirmed it was ephedrine.
Customs and Border Protection compliance and enforcement director Karen Harfield said shipping the drugs in the rice was an unusual and sophisticated method.
Her officers went through the laborious process of separating the drugs from the rice in a "slightly more sophisticated" process than using a kitchen sieve, she said.
Police tracked the delivery of the consignment to a storage facility in Melbourne later in July and then its movement to Sydney on August 5.
On Monday, they executed nine search warrants in Melbourne and Sydney, seizing $255,000 in cash and leading to the arrests.
