Twenty tigers and one leopard have died since early September at Mango Garden eco-resort in Dong Nai province.

The animals refused to eat, showed fatigue, and had fever after eating chicken meat and chicken heads provided by a local company, Xinhua news agency reported quoting the Vietnam News Agency

Phan Van Phuc, head of the Department of Infectious Disease Prevention and Control at the Dong Nai Center for Disease Control, said it was likely that the deceased tigers were infected with the H5N1 virus from infected chicken meat.

Authorities are tracing the origin of the chicken to determine the infection source, he said.

The zoo has disinfected the enclosures and isolated the tiger zone to prevent further outbreaks, according to VnExpress.

The resort has been asked to restrict visitors and monitor the health of 30 people having close contact with the infected animals.

The Ministry of Agriculture and Rural Development has recently reported sporadic cases of avian flu among poultry in several localities.