Hundreds of people fell ill, and at least one person died, after eating beef in a village in Meo Vac district in the mountainous Ha Giang province near the Chinese border late last month, local newspapers have reported.
Vietnam's National Institute of Hygiene and Epidemiology was testing whether the outbreak was caused by anthrax, institute official Le Quynh Mai told AFP.
"There are 13 suspected cases of anthrax found recently in Ha Giang province, and we have received seven specimens to be tested here," she said.
Mai confirmed that one person had died but stressed that "the result of our tests is not available yet."
Local newspapers said large numbers of cows, pigs and goats had died in the region since late June, and that local people had complained of skin ulcers, vomiting and fever after eating meat from infected animals.
Anthrax, a bacterial spore that can lie dormant in animal feces in the soil, attacks people's skin, lungs and digestive systems.
Humans can be infected with anthrax -- which has also been used to develop biological weapons -- through eating undercooked meat from infected animals or handling animal products such as wool.
In gastrointestinal anthrax, which causes nausea, bloody diarrhea, fever and severe stomach pain, between one quarter and half of infections are fatal, according to the US Centers for Disease Control website.