SHANGHAI - Three deer at the Shanghai Zoo died in May with large masses of inedible objects, including plastic bags and towels, found in their stomachs, said zoo authorities.

The three deer died suddenly on May 10, May 20 and May 21. Each was found to have around six kilograms of inedible material in its stomach. The plastic and towels were wrapped around food thrown by zoo visitors to feed the deer.

"For years, the zoo has put much effort into educating visitors to behave in a civilized manner. However, it is still hard to ban visitors from feeding animals irresponsibly, which means that some visitors still lack respect and understanding for the animals," said Pei Enle, head of the zoo.

In 1993, a giraffe died after eating visitors' plastic bags at the Shanghai Zoo, leaving her newborn baby screaming in pain. The zoo built a pavilion to display the preserved giraffe to warn visitors against harming animals.

China is amending its wild animal protection law, which was first adopted in 1998 and amended in 2004, to better protect wild animal species and guarantee their welfare.