NANJING, Jan. 2 (Xinhua) -- Customs officials in east China's Jiangsu Province said Tuesday they had caught a gang suspected of smuggling frozen food valued at 200 million yuan (31 million U.S. dollars).

Four people have been detained from the gang, which allegedly has smuggled 8,000 tonnes of frozen shrimp, cuttlefish and fish fillets since July 2013.

The food was found to be smuggled from the China-Vietnam border and then sold in the cities of Wuxi and Suzhou, said an official with the customs of Nanjing, the provincial capital.

More than 100 tonnes of smuggled frozen food was also seized, said the official.

Further investigation is under way.

Chinese customs launched an anti-smuggling campaign in 2017. As of the year end, Nanjing customs had seized more than 4,700 tonnes of smuggled cotton, over 1,200 tonnes of white sugar and 9,000 tonnes of frozen food.