Customs officials in Xiamen, Fujian province, have revealed details of the two largest ivory smuggling cases in China, two years after they convicted the leaders of the smuggling operations, the Strait Herald reported on Tuesday.

The report said two smuggling gangs were identified by investigators, with nearly 12 metric tons of ivory worth 603 million yuan ($98.84 million) seized.

One gang was led by an ivory carver surnamed Chen, while the other was led by a man surnamed Liu.

Customs officers confiscated 2,154 elephant tusks and associated ivory products from Chen's gang, weighing 7.68 tons, with a total value of 378 million yuan. Meanwhile, 1,034 tusks were retrieved from Liu's group, weighing 4.2 tons and valued at 225 million yuan.

The report says that the tusks were hidden in among leather goods, construction materials and consignments of copper.

Chen, a carver with a certified ivory shop in Putian, Fujian province, who was not satisfied with the fixed quota of legal tusks, used a customs broker to get illegal tusks from African countries.

Chen was sentenced to 15 years in prison on Nov 14, 2011.

Xiamen customs cracked Liu's gang on Nov 8, 2011 when they seized two trucks containing tusks.

In 1981, China joined the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

In January and February this year, China led a cross-continent operation code-named "Cobra" to crack down on the illegal wildlife trade, with 22 Asian and African countries taking part.

The cross-border operation uncovered more than 200 cases involving trafficked wildlife parts and led to the detention of more than 100 criminal suspects.