Australian authorities Wednesday said they had uncovered a major 274 kilogramme (600 pounds) haul of the stimulant ephedrine, used to make crystal methamphetamine, during a pest check on a rice shipment from India.

The seizure is one of the largest of ephedrine in Australia, with enough of the drug to manufacture 200 kilogrammes of crystal meth -- also known as ice -- worth up to Aus$200 million (US$188 million), Customs said.

The crystalline substance was scattered throughout bags labelled "basmati rice" which arrived in a 3,600-packet consignment in Melbourne in July, and were physically checked for pests by a biosecurity officer.

"The officer who did the inspection was really on the ball," Agriculture Department first assistant secretary for border compliance 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."

Three people -- two Canadians and one Australian -- were arrested and charged over the alleged importation and intended distribution of the ephedrine after the bags were delivered to their destinations in Sydney and Melbourne.

An Indian national, allegedly responsible for organising the ephedrine and sending the consignment to Australia, was also detained in India by local police.

Australian Federal Police national manager for crime operations Ian McCartney said the seizure had dismantled a multinational syndicate.

Customs and Border Protection compliance and enforcement director Karen Harfield said hiding the drugs in rice was an unusual method and forced her staff to laboriously sift out the substance from the white grains.