This route was in addition to one in which illegal frozen meat was smuggled from the Americas through Hong Kong and Haiphong and onto Guangxi’s border city of Dongxing and Guangzhou in Guangdong.

Frozen beef is a key ingredient of Chongqing- and Beijing-style hotpot.

News of the smuggling routes comes amid a crackdown by Chinese customs across 14 provinces this month that seized more than 100,000 tonnes of frozen chicken, beef, pork and other meat, worth over 3 billion yuan (HK$3.8 billion). More than 20 groups of smugglers have been detained.

In one operation, in Changsha, Hunan province, the frozen meat – some of it more than 40 years old – had been smuggled into Guangxi via Hong Kong.

A customs investigation in Chongqing, which began last May, found at least 8,130 tonnes of beef smuggled along the route from India had been received by a wholesaler and sold on to hotpot restaurants from June 2013 to last July, Thepaper.cn reported. It said the main suspect, from the mainland, would stand trial along with 16 family members. Another suspect, from Vietnam, was at large.

“The beef arriving in Vietnam was treated as re-exported meat, so was charged the minimum tax rate – far below China’s level of import tax,” an industry insider was quoted as saying.  

Professor Cao Binghai, of Chinese Agricultural University, said up to two million tonnes of beef had been smuggled into China in 2012 and 2013.

Each kilogram of boneless buffalo meat was worth about 21 to 24 yuan in 2013 when exported from India to Vietnam, but its wholesale price on the mainland at the time was between 56 and 59 yuan per kg, partly due to taxes amounting to 39 per cent.

Guangzhou-based food critic Lao Yibo said the muscle fibre of aged frozen meat was darker and meat that had been refrozen appeared watery when served. He recommended diners choose light cuisine and avoid heavily marinated or strongly flavoured hotpots.