HANOI, Vietnam -- Authorities in Vietnam seized more than a ton of live snakes that were smuggled in on an airplane from Thailand, officials said Friday.

Thousands of nonvenomous rat snakes were shipped as cargo in 60 boxes on a Vietnam Airlines flight from Bangkok to Hanoi's Noi Bai airport Thursday, said airline spokesman Trinh Ngoc Thanh.

Thanh said the shipment had been declared as live fish.

Many of the snakes, which were surrounded by plastic filled with ice water, have died, said Nguyen Ba Oanh, director of the Wild Animal Rescue Center near Hanoi where the snakes were taken. The reptiles each weighed between 200 grams (.44 pounds) to 3 kilograms (6.6 pounds).

The official Vietnam News Agency reported Friday that the snakes, which are protected animals, may have been en route to another country.

Last month, Vietnamese authorities also found some 700 kilograms (1,540 pounds) of dead snakes on a Thai Airways flight from Bangkok.

"Obviously, there was some problems with cargo inspection at the Bangkok airport," Thanh said "We plan to send a letter to the Bangkok airport authorities urging them to enhance inspection to avoid this incident from happening again."