Authorities in the northern province of Quang Ninh said four more bears have died at a private farm due to starvation.
The deaths were reported on Monday, less than two months after four other bears were starved to death at the same bear farm, Nong Trang, whose main income source has been cut off by a ban on bile extraction.
Owner Nguyen Trong Bo said there are only five bears left in his farm, compared to around 40 at the busiest time.
All the deaths were due to starvation, Bo admitted.
He said he had paid VND80 million (US$3,748) for each of the bears.
The man claimed that after the government banned private bear farms from extracting bear bile to sell to tourists in May 2014, he could no longer afford to feed the animals.
A worker at the farm said that the bears were fed with one small meal a day which includes vegetables and mash feed used in pig farming.
Previously when bears were farmed for bile, they used to be fed with stewed pork bones and pumpkin, the worker said.
Vietnam's agriculture ministry in late January ordered the province to help rescue captive bears at local farms, following reports of mistreatment of the animals.
The new deaths seem to suggest that no rescue efforts have been made.
Another farm owner said local authorities have not ever discussed with farm owners about financial support for them after the ban.
Pham Thuy Trinh of Hong Kong-based animal welfare group Animals Asia Foundation said the NGO is not allowed to negotiate financial support with farm owners in exchange for the bears.
According to Lao Dong newspaper, 108 bears in Ha Long private farms starved to death in 2014.
It is estimated that there are some 50 bears left at private farms in Quang Ninh.