Police officers in Harbin unload an absorbent material that arrived from Hebei Province yesterday. Some 1,200 tons of the chemical were shipped from Hebei and Shanxi provinces to help purify pollutants choking the Songhua River.

The main wave of polluted water from a chemical plant explosion in northeast China began flowing past the city of Harbin yesterday as environmental officials continued efforts to clean up the Songhua River and ensure safe drinking water for millions of residents.
Sixteen kilometers upstream from Harbin's water intake, the density of nitrobenzene, one of the major pollutants, was more than 30 times above safe levels, according to the State Environmental Protection Administration.
The capital of Heilongjiang Province shut off its tap water system on Wednesday as a health precaution, and is trucking in water and digging new wells to supply its 3.8 million residents.
Other cities along the Songhua were forced to take similar action after an explosion on November 13 at a China National Petroleum Corp plant in Jilin Province. The blast released 100 tons nitrobenzene and benzene into the river, creating an 80-kilometer-long slick of poisoned water and raising fears as far away as Russia.
A work group from the State Council, China's cabinet, planned to leave Beijing yesterday for Harbin to investigate the environmental catastrophe.
At a news conference on Thursday, a senior environmental protection official said the CNPC plant should be held responsible for the river pollution.
As part of the cleanup effort, the Ministry of Water Resources ordered two reservoirs along the Songhua to increase discharges into the river in an attempt to dilute the chemical slick.
An official with the ministry said yesterday that the river's flow is slow at present because it is the dry season and freezing has begun.
Some 1,200 tons of carbon absorbent material arrived in Harbin yesterday to help sop up the pollutants in the river.
The material was sent from Hebei and Shanxi provinces in north China and Ningxia Hui Autonomous Region in northwest China.
"This came just in time," said Zhang Zuoji, governor of Heilongjiang, when shaking hands with a truck driver who transported the first shipment of carbon arriving from Tangshan, Hebei Province, yesterday afternoon.