HANOI, Vietnam >> More than a dozen tigers were incinerated after the animals contracted bird flu at a zoo in southern Vietnam, officials said.

State media VNExpress cited a caretaker at Vuon Xoai zoo in Bien Hoa city saying the animals were fed with raw chicken bought from nearby farms. The panther and 20 tigers, including several cubs, weighed between 20 and 265 pounds when they died. The bodies were incinerated and buried on the premises.

“The tigers died so fast. They looked weak, refused to eat and died after two days of falling sick,” said zoo manager Nguyen Ba Phuc.

Samples taken from the tigers tested positive for H5N1, the virus that causes bird flu.

More than 20 other tigers were isolated for monitoring. The zoo houses some 3,000 other animals including lions, bears, rhinos, hippos and giraffes.

The 30 staff members who were taking care of the tigers tested negative for bird flu and were in normal health condition, VNExpress reported.

Bird flu has caused hundreds of deaths around the world, the vast majority of them involving direct contact between people and infected birds.