Border guards in the northern province of Lao Cai on Sunday confiscated 2.1 kilograms of heroin from a minibus, taking eight passengers into custody for investigation, Vietnam News Agency reported.
Leaders of Lao Cai Border Guards' Headquarters were quoted as saying that they found the drugs in a rice sack on the bus, which frequently operates on the route from the northern province of Lai Chau to Lao Cai.
Eight passengers were on board then, but so far no one has admitted their possession of the sack, the leaders told the news agency.
According to the headquarters, the bust, which was conducted in cooperation with Lao Cai's customs following information provided by locals, was the province's largest since the beginning of this year.
The case is being investigated.
Vietnam has some of the world's toughest drug laws. Those convicted of smuggling more than 600 grams of heroin are eligible for the death sentence.