Three smuggling gangs have been busted for bringing over 72,000 tons of used laptops and parts into China illegally, customs have said.

In cooperation with police, customs authorities in Guangdong Province, Liaoning Province and Tianjin Municipality arrested 54 gang members in a raid on January 5, an official with the General Administration of Customs said.

More than 500 police officers took part in the raid and seized 185 shipping containers, as well as more than 200 additional tons of products at the site.

Investigations showed the gangs had smuggled more than 72,000 tons of "e-trash" since 2013, the largest quantity ever discovered, which was hidden in over 2,800 containers. The e-trash came from Japan and some European and American countries, said the official.

Sun Hongyan, an official working at Dalian customs in Liaoning Province, said that the smuggled e-trash like electric fans, computers and mobile phones would be disassembled and sorted and then renovated to sell in second-hand market in different regions. There is no quality assurance for such products, China Central Television reported Tuesday.

Other than the renovated ones, some of the waste electronic units like PC motherboards will be sold to small workshops to extract noble metals. However, such refining processes could generate severe environmental pollution.

Unlicensed workshops use acids to corrode the electric parts and then discharge the acids without proper processing measures for environmental protection, Sun said. As a result, groundwater, soil and air have been polluted and even become toxic.

Guiyu, Guangdong Province, one of the largest e-trash processing places in China, has thousands of workshops and over 60,000 people working in processing e-waste, Xinmin Weekly reported last July. A study by Shantou University showed that newborn babies in polluted areas have excess amounts of heavy metals in the body. The study also showed that children between 3 and 4 have lower IQs than children in nearby towns.

Guangdong customs authority has launched a campaign to crack down on smuggling e-waste since last year and a total 976,300 tons of solid waste was captured.