They believe that a Chinese man, 56, is the leader of this drug ring, and that he was operating under the cover of a garment firm in the outlying Binh Tan District.
According to the Ministry of Public Security's Drug Crime Investigation Department, the ring was smuggling meth from the Golden Triangle into Vietnam before distributing it across the country.
Investigators said the garment company, Hasan, is registered in the name of a Vietnamese woman in her 40s, believed to be a girlfriend of the Chinese drug lord.
They said that in the five years since Hasan was established, it had only 40 customs declaration forms for garment products, which made police suspicious.
Members of the ring rented apartments or stayed in hotels near the company.
The company hired Vietnamese guards, but no one was allowed to know what they were guarding, they said.
Every time the "goods" arrived, the guards would be told to stay away.
After a long period of surveillance, a raid was carried out on Wednesday by officers from the Drug Crime Investigation Department in coordination with the Southern Border Guard's Special Forces, and police from HCMC and the Central Highlands province of Dak Nong.
Dozens of armed mobile police officers, plainclothes policemen and border guards raided the mansion behind the company. The mansion was being used as a hideout and warehouse by the drug trafficking gang.
Among the 20 or so people arrested during the raid were three Vietnamese and 16 Chinese. A specific number of suspects was not given.
Wednesday’s seizure of 300 kilos of methamphetamine worth VND600 billion ($26 million) is said to be the largest drug haul ever in HCMC.
The drug is believed to have originated from Laos and smuggled into Vietnam through roads around the Bo Y Border Gate in the Central Highlands province of Kon Tum. The shipment was slated for delivery to Taiwan.
Police said they found many sacks that are of the same type as the ones they’d collected from previous drug busts in the central and Central Highlands regions.
On February 17, police had detained Vangchueyang Briachear, a 25-year-old Lao man, when he was on his way to bring 294 kilograms of meth from Laos to Vietnam.
Earlier, in October last year, police arrested Xeng Vang, 23, also from Laos, when he was driving a truck carrying 300 kilos of meth from Ha Tinh to Da Nang in the central region.
The public security ministry is working with local police in different provinces and cities to expand the investigation.
Vietnam is a key trafficking hub for narcotics around the Golden Triangle, an intersection of China, Laos, Thailand, and Myanmar and the world's second-largest drug producing region.
It also has some of the world’s toughest drug laws. Those convicted of possessing or smuggling more than 600 grams of heroin or more than 2.5 kilograms of methamphetamine face the death penalty.
While heroin has long been common among users in Vietnam, the use of synthetic drugs like meth or ecstasy is on the rise, especially among youth.
Seven people died after using drugs at an electronic music festival in September last year in Hanoi, sparking off an alarm and prompting tougher crackdowns.