Environmental authorities from China and Russia held a closed-door meeting Wednesday in Harbin, capital city of north China's Heilongjiang Province, to discuss the rehabilitation of the polluted Songhua River, which flows into a Sino-Russian border river.

Wednesday's session focused on furthering cooperation between the two countries in controlling pollution on the river. The Songhua is the largest tributary of the Heilong River, known in Russia as the Amur River.

Officials from both sides also discussed the protection of biological diversity in the Amur River basin.

The results of the discussion will be announced on Thursday.

The 1,900-km-long Songhua River originates in the neighboring province of Jilin and flows into the Heilong River, which runs along the Sino-Russian border.

In November 2005, about 100 metric tons of industrial waste spilled into the Songhua River after a chemical plant explosion in Jilin Province, which caused cities along the river to cut water supplies to 3.8 million people.

The government launched a five-year campaign in 2006 to clean up the river and remove harmful pollution resulting from the explosion.

China has built 222 pollution control projects, including sewage treatment plants and water recycling facilities, along the river over the past five years as part of the campaign.

China's environmental protection minister Zhou Shengxian said Tuesday that the water quality of the Songhua River has improved over the last five years, with pollution levels dropping significantly.

Zhou said that China will step up efforts to fight pollution in the river over the coming five years by building more sewage treatment plants and shutting down heavily-polluting factories in the area.

Over the past five years, China and Russia have conducted 12 rounds of joint water quality monitoring for three cross-border rivers and one cross-border lake.