This year, customs authorities and the ministries of environment and commerce launched a crackdown which saw hundreds of suspects detained for smuggling solid waste into the country, the government said.

On Dec 19, customs officers in 13 provinces and regions, including Guangdong, Zhejiang and Jiangsu－major centers for the processing of imported recyclables－detained 127 suspects from 47 gangs in the largest operation of the year, according to a statement issued by the General Administration of Customs.

More than 323,000 metric tons of what was referred to as "foreign garbage", including plastic scraps and waste mineral residue, had been seized by 10 am on Dec 19, it added.

In recent decades, China has imported recyclable waste to process and reuse as raw materials for the manufacturing sector, but the phrase "foreign garbage" refers to solid waste on a list of prohibited products smuggled into China, along with waste that was imported without permission.

The importation and processing of the material can cause severe pollution that may be hazardous to human health, resulting in the central government prioritizing its elimination.

Since 2013, customs officers nationwide have investigated about 400 cases of solid waste smuggling and detained more than 800 suspects, according to a report submitted to the Standing Committee of the National People's Congress, the nation's top legislative body, last month.

This year, customs nationwide have detained 421 suspects from 298 gangs accused of smuggling solid waste, equal to half the number apprehended in the past five years.

In addition, 1,700 inspectors from the Ministry of Environmental Protection conducted a month-long inspection of recycling companies during July.

Sixty percent of the 1,792 recycling companies in the country were found to have violated relevant laws and regulations, according to Li Ganjie, minister of environmental protection.

Most of the violations were related to the excessive discharge of pollutants, failure to adhere to restrictions on the importation of recyclables and improper treatment of solid waste, according to a statement issued by the ministry.

As a result, the ministry and local environment authorities punished 940 companies, detained managers at 32 of them and closed down 94 businesses.

"Between 2018 and 2020, we will maintain the strict supervision of domestic recycling plants that process imported solid waste and conduct special inspections annually to ensure companies obey the law," Li said.

Before the end of the year, ministry officials will again visit the companies that were inspected, and impose heavy punishments on any that have failed to follow the correct pollution-reduction measures, he added.