Chinese customs cracked a diamond smuggling case earlier this month in which an estimated 3.88 billion yuan ($573 million) worth of diamonds had been smuggled since 2015, according to an announcement by the General Administration of Customs on Monday.

On Sept 1, 10 customs offices around the country sent more than 1,000 police officers to crack down on the smugglers.

The anti-smuggling department of customs arrested 121 suspects and seized over 2,520 diamonds, more than 4,000 carats of broken diamonds and 158 pieces of diamond jewelry.

The preliminary investigation found that suspects on the Chinese mainland ordered diamonds from a number of overseas diamond suppliers. Smugglers responsible for collecting and transferring the diamonds would smuggle the goods into the Chinese mainland through Shenzhen's Luohu and Huanggang ports, which connect Shenzhen and Hong Kong. The diamonds were either carried across the border by individuals or hidden in trucks or private cars that had license plates for both Hong Kong and Guangdong province. Then the goods would be delivered either directly to the buyers or through express delivery services.

The General Administration of Customs stressed that customs will continue to strengthen inspection and supervision to crack down on diamond smuggling, and will strengthen comprehensive governance and work with local governments and industry associations to promote the sustained and healthy development of relevant industries.