The seizures announced Monday were conducted during a three-month operation that centered around Lwe Kham village in Kutkhai Township in Myanmar's northeast Shan state. Thirty-three suspects were arrested.
Jeremy Douglas, the regional coordinator for the United Nations Office of Drugs and Crime (UNODC), said the scale of the seizure was "truly off-the-charts."
They also seized nearly 3,750 liters (990 gallons) of liquid methylfentanyl, which is a powerful synthetic opioid like fentanyl. It is believed to be the first time authorities have discovered such a massive amount of fentanyl or one of its analogues in Southeast Asia.
The region has so far been spared an opioid crisis like that in the United States, but experts have warned that drug producers in Asia may eventually chose to supply those who use opiate drugs like heroin with synthetic opioids, which are made to mimic the chemical structure of poppy-based drugs.
Douglas said that the amount of methylfentanyl precursor seized could have been used to produce a batch of synthetic opioids large enough to replace the region's heroin production for a year.
"This may be the moment we have feared -- synthetic opioids are in the region in a big way," he said.
A meth boom
They've also been able to operate with relatively little interference from police by moving production into the Golden Triangle, the border area where Thailand, Laos and Myanmar meet. The Golden Triangle was for years the world's biggest heroin-producing region, and today it is still notorious for its lawlessness -- especially on the Myanmar side, which is in some parts governed by local militias and warlords.
The result has been an unprecedented boom in the synthetic drug trade. The methamphetamine market in East and Southeast Asia alone is worth as much as $61.4 billion a year, the UNODC said in a report released Friday.
The market is so strong that even the novel coronavirus outbreak appears to have done little to impact synthetic drug production and trade.
"While the world has shifted its attention to the COVID-19 pandemic, all indications are that production and trafficking of synthetic drugs and chemicals continue at record levels in the region," Douglas said.
Douglas said the operation provided further proof of the increasing size, scale and sophistication of Asia's drug cartels.
"It is clear that a network of production facilities like those found would not be possible without the involvement and financial backing of serious transnational organized criminal groups," Douglas said in the joint statement.
Burmese authorities seized about 18 tons of meth, though most of it was in cheaper pill form, and drugs usually fetch a higher price in Australia then they do in Southeast Asia.
This story has been updated to better reflect methylfentanyl's relationship to fentanyl