SHANGHAI (Reuters) - China has tightened a ban on solid waste imports, the official Xinhua news agency said, part of the country’s “war on pollution” which has seen a series of measures to curb imports of scrap this year.

The state news agency, citing a government document, said late on Sunday that imports of 32 types of solid waste would be banned from Dec. 31, including hardware, ships, auto parts, titanium, wood, and stainless steel waste and scrap.

China’s scrap imports have tumbled this year as the country has ratcheted up bans and cracked down on smugglers. Earlier in the year China clamped down on imports of scrap metal, paper and plastics, as a part of a campaign against “foreign garbage”.

China has tightened its list of solid waste imports several times in the past year and has previously announced plans to cut permitted waste imports to 18 types by the end of 2019 from 66 in 2017.