A monthlong environmental inspection of seven provincial regions, including Shanxi and Liaoning provinces and Tianjin, found more than 28,900 pollution problems and led to the detention of 355 people by the time it finished on Sunday, authorities reported on Tuesday.

It was the third round of inspections headed by the State Council, China's Cabinet, since 2016. Additional inspections will be conducted this year around the country. Among the provincial regions to be covered in the next rounds are Zhejiang and Sichuan provinces.

In the most recent inspection, central government inspectors received 35,523 reports from the public, of which some 82 percent, or 28,966 reports, were found to involve pollution problems and transferred to the involved provinces and city governments for further investigation, the Ministry of Environmental Protection said on Tuesday.

"The governments involved have required more than 20,000 polluting companies to halt excessive levels of pollution and improve technologies and equipment. The total fine has reached 336 million yuan ($49 million)," the ministry said in a statement.

It said the 355 people detained were accused of contaminating the environment, and some received administrative detention while others involved more serious cases.

Also, 4,018 officials from the governments in those areas were held accountable for their ineffective performance in protecting the environment, it added.

In the seven inspected regions - Liaoning, Shanxi, Fujian, Anhui, Hunan and Guizhou provinces and Tianjin - it was Shanxi, where coal and heavy industries are a key economic pillar, that had 88 million yuan in fines, the largest amount for one region, the ministry said.

High-level environmental inspections are especially effective because the inspectors have sufficient clout to talk directly with provincial leaders about the problems, unlike inspectors led by the ministry, officials said.

Chai Fahe, a researcher at the Chinese Research Academy of Environmental Sciences, said previous inspection rounds pushed provinces to deal with long-standing problems such as upgrading the industrial structure to control the expansion of heavily polluting industries in Hebei province.

Hebei, the first province to be put under central environmental inspection, in January 2016, has stopped releasing reports on the estimated economic costs of environmental protection since the environment has been given a priority position in the province.

The environmental improvements made by the province following the central inspections were listed among its achievements last year.

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