Police from the Ministry of Public Security rescued 350 kilograms (some 773 pounds) of live pangolins in Quang Ninh Province on Monday, before they could be force fed and smuggled across the border to China.
One worker said hundreds of pangolins are smuggled into China every day after being gathered in Quang Ninh to be force fed a rice flour solution that increases their weight (and, subsequently, their price), Tuoi Tre newspaper reported.
Pham Long, a 43-year-old member of the smuggling team, said he and five others were tasked with stuffing the animals with between 300 to 500 grams of the solution.
Police seized a car whose seats had been removed to make space for the animals.
They also questioned a Chinese woman at the scene named Tang Ming Yan, 48.
Yan was listed on an invoice as the recipient of the shipment, though police say they're still investigating her role in the scheme.
Pangolins, also known as anteaters, are protected under both the Convention on International Trade in Endangered Species (CITES) and Vietnamese law.
The laws carry punishments of up to seven years and fines up to VND500 million (US$23,720) for those who trade, kill, capture or hunt protected animals
Long said one or two cars head to China every day, loaded with 300 to 500 kilograms of pangolins.
One vehicle intercepted on Sunday had been loaded down with nearly a metric ton of the creatures.
Other workers said the animals were brought from Ho Chi Minh City and the central province of Ha Tinh.
Pangolins are sought by illegal wildlife traders for their meat and scales, which are used in traditional medicines.