A senior Chinese environment official has said almost all the chemical barrels washed into a major river last week have been recovered and the retrieval operation is winding up.

Vice Minister of Environmental Protection Wu Xiaoqing told Russian environment officials the operation to clear the barrels from the Wende River, in northeast China, was in its final stage and the water quality remained normal, according to a report in Friday's China Environment News.

Wu told Russia's Ministry of Natural Resources and Ecology that 7,107 barrels had been collected and disposed of, including 3,633 that were filled with chemical materials.

Wu said the operation had "achieved decisive victory" and was about to end, although the report in the China Environment News did not say when exactly it would be called off.

"China has adopted resolute measures to prevent these chemical barrels from floating into Heilongjiang Province, and they won't affect Russia at all," Wu was quoted as saying by the paper, which comes under the Ministry of Environmental Protection's administration.

A total of 7,138 chemical barrels were swept into the Wende River, a tributary of the Songhua River, which forms part of China's border with Russia, after floods destroyed two chemical plant warehouses in Jilin City, Jilin Province, last week.

A total of 3,662 barrels were filled with colorless and highly explosive chemicals, mainly trimethyl chloro silicane and hexamethyl disilazane.