Major Japanese retailer Ito-Yokado Co. has asked tenants at its shopping malls to stop selling ivory products, joining a growing list of Japanese companies that have banned such sales amid international efforts to stamp out African elephant poaching.

According to a company official, the supermarket subsidiary of retail giant Seven & I Holdings Co. has already stopped selling ivory products at its own stores and has asked tenants at shopping malls that it operates to follow suit.

The official declined to elaborate on details such as when the ban will begin.

International ivory trading has been banned since 1990 under the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention.

The prohibition had been credited with replenishing the population of African elephants, which remain classified as a species that may become endangered, but the resurgence in poaching in recent years led member states of the convention to push to shut down domestic markets in 2016.

A number of major businesses have already denounced the sale of ivory items including e-commerce firms Rakuten Inc. and Mercari Inc., and retail giant Aeon Co., citing international calls for closing ivory markets.

The Japanese government remains opposed to closing its market, however, arguing that ivory products being traded in the country were imported before international regulations came into force and related businesses are properly controlled.

Ivory has long been used in the country to make hanko stamps, though alternative materials are now widely used.