Green tea maker says its packaging can be traced to shed light on how smugglers obtained it

A record haul of 3.9 tonnes of liquid ephedrine shipped to Sydney from Thailand in Oishi tea cartons sits in a warehouse in Sydney. It was the largest-ever seizure of precursor chemicals at the Australian border. (Australian Federal Police photo via AP)

Oishi, the country's biggest producer of ready-to-drink green tea, says it will cooperate fully with authorities investigating a huge seizure by Australian authorities of methamphetamine ingredients concealed in Oishi bottles and cartons.

"In reference to the recent appearance of our product packaging in the news, we will fully cooperate with the investigating agencies both domestic and overseas," Oishi said in a statement released on Saturday. "Our world-class production and supply chain processes incorporate a traceability system that will provide all necessary information.''

The company, owned by billionaire Charoen Sirivadhanabhakdi, released the statement after news emerged this week of the seizure of 3.9 tonnes of ephedrine, a methamphetamine precursor, by Australian authorities.

Australian Federal Police (AFP) said two people were arrested after the seizure last month at a Sydney sea cargo examination facility. An Australian man and a woman with Australian-Chinese dual nationality, both 22, were refused bail on Thursday after being charged with importing a drug precursor.

Australian Border Force officers, following up on information from Thai authorities, detected the shipment of more than 1,000 cartons, each containing 24 bottles labelled as iced green tea and black tea. Tests were positive for ephedrine in around one-third of the cartons, the AFP said. The shipment was mislabelled as products from the popular Oishi brand.

The liquid ephedrine could have been used to make up to A$3.5 billion worth of methamphetamine, police said.

The Office of the Narcotics Control Board (ONCB) said the suspects were believed to be part of a drug ring active in the Golden Triangle, the overlapping mountainous area shared by Thailand, Myanmar and Laos. The area is notorious for drug production, but some operators are now moving methamphetamine production abroad and Australia has emerged as a favoured location, according to the ONCB.