Chemicals have been detected in a river in northeast China's Heilongjiang Province four days after floods swept 3,000 chemical-filled barrels into a major river, local officials said Sunday.

Chemical-tainted water was found at Guqia Port, Zhaoyuan City, on the Songhua River near the Heilongjiang-Jilin border, said Du Jiahao, executive vice governor of Heilongjiang, adding that the tainted water first flowed into the province at about 7:00 PM Saturday.

But the water in the Songhua River, a major drinking water source for millions, is still safe, officials said, citing results of water quality tests.

Tests have found trimethylsilanol in the river water, indicating the tainted water has arrived in Heilongjiang, said Li Ping, director of the provincial environmental protection department.

"Our conclusion is that the water in the Songhua River is not contaminated and that it is safe for drinking. Biological toxicity tests show the water is safe," Li added.

Ministry of Environmental Protection tests also show the river's water quality "within a normal range," ministry spokesman Tao Detian told Xinhua Sunday.

Tests conducted in Jilin have shown "a very small quantity" of hexamethyl disiloxane in the water.

Environmental specialists said the level of chemicals in the water "poses no threat" to public health and that the environmental impact of the accident is "negligible."

Some 3,000 chemical-filled barrels and 4,000 empty barrels were swept into the Songhua River Wednesday morning after floods hit the warehouses of two chemical companies in Jilin City, Jilin Province.

Each chemical-filled barrel contains about 170 kilograms of either trimethyl chloro silicane or hexamethyl disilazane.

Workers had retrieved 5,365 barrels -- some filled, some empty -- by 9:30 AM Sunday.

Hundreds of soldiers, armed police and firemen are stationed at Guqia Port to intercept the barrels.

Boats are chained together across the 500-meter wide waterway to block the passage of the barrels.

Emergency workers have also prepared a 400-meter-long oil spill boom to to contain any contaminated water.

The 1,900-kilometer-long Songhua River is the largest tributary river for Heilongjiang River, which in places traces the China-Russia border.

The river is a source of drinking water for cities in Jilin and Heilongjiang.

The incident has revived memories of an explosion in 2005 at a petrochemical plant in Jilin Province. The accident contaminated the Songhua River and left 3.8 million people in Harbin without drinking water for four days.

In a similar accident Friday, 1,500 sealed drums containing oil, resin and fertilizer sunk in floodwaters in the central China city of Wuhan, on the Yangtze River.

But all the drums have been safely retrieved and the water quality of the Yangtze River was not affected.

Police have arrested the people responsible for the improper storage of the drums.

(Xinhua News Agency August 2, 2010)