By Saturday they had seized 38 kilos of narcotics from the gang.
They had been surveilling Bui Pham Duy, 36, of Hoc Mon District for a while, and last Tuesday followed him on suspicion he was going for a drop.
Officers caught him meeting Nguyen Thi Xuan Van, 29, near a school in Hoc Mon and handing over a package.
They jumped in and caught them in the act.
Inside were four kilograms of methamphetamine, half a kilo of ketamine, a synthetic drug, and 5,000 ecstasy pills.
They then searched Duy’s home and found 20 kilos of meth, 15,000 ecstasy pills and six kilos of ketamine.
The gang, run by Duy and Nguyen Hong Chau, 32, another local, has been trafficking drugs into the city from Cambodia for years.
Vietnam 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 methamphetamines face the death penalty. The production or sale of 100 grams of heroin or 300 grams of other illegal narcotics is also punishable by death.
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.