Alibaba.com has expanded its list of banned animal products after an environmental group found several merchants using the international trading website were selling leather made from manta ray skins.

Manta rays and several others species that were named last year as threatened by a special United Nations convention can no longer be traded on the website.

Like sharks, rays are under increasing pressure from fishermen who harvest them for their body parts. The distinctive gill rakers of rays are used in Asian medicines and their skin is used in exotic leather products.

“Alibaba.com takes animal conservation seriously and has already banned shark fin, bear bile and their byproducts from our platform,” said company spokeswoman Pam Munoz. The website’s policies are broadly governed by the international Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) treaty, which lists more than 35,000 endangered species, along with the laws of some countries.

Manta rays, about which little is known, slipped through the CITES net and are not listed as endangered. But last year, representatives of more than 80 countries attending a UN conference on the conservation of migratory species named the giant manta ray and six other species as threatened and in need of conservation. Fishing for devil rays, including mantas, skyrocketed in the last decade, according to the UN.

Munoz said Alibaba.com amended its product-listing policies to include animals named by the UN as well as all species in the devil ray family after an ocean conservation group, Oceana, posted a blog item alerting members that manta ray skin was being sold on the website. “Our intention is to protect endangered animals and we found that our listing rules were not clear on that front, so we clarified our listing rules to also protect animals under UN policies,” Munoz said.

Two product listings for manta rays and their leather were removed from Alibaba.com. The website also changed its software used to identify and filter out banned products to conform with the expanded list.

Alibaba.com has more than 25 million members worldwide.