The monkeys found being illegally transported in Con Dao Island on September 30.
Forest rangers at the Con Dao National Park saw Nguyen Minh Phong, 38, transporting four baskets containing the monkey from a local forest to Ben Dam Beach at 2.30 pm on September 30. Phong left the monkeys and ran away after seeing the forest rangers but he was then arrested.
Authorities found 17 long-tailed monkeys, 10 of them dead already and seven others in weak health condition, in the four baskets. The monkeys weighed a total 33.5 kilos.
Phong said that he had been hired by a neighbour to transport the monkeys to the beach for a boat to take them to shore for sale. He said he didn't know where the monkeys came from.
Phong has been fined for the illegal transportation of rare endangered animals and the monkeys were detained for investigation.
Long-tailed monkeys, whose scientific names are Macaca fascicularis, belong to a rare and critically endangered wild animal group.
Many residents and tourists have been fined or prosecuted for transporting, trading, and hunting wild animals in Con Dao forests.