Environmental protection officials have declared the land and waterways surround a northeast China chemical plant that blew up last week to be safe from major pollution damage.

The blast on April 6 in Harbin, capital of Heilongjiang Province, had left no major environmental problem, said provincial government officials on Monday after four days of close monitoring.

The Xinguang Chemical Plant, which had produced 20 tons of diluting agents each year, is only 4 km from the Songhua River, which joins the Heilongjiang River and flows into the Amur River in Russia.

The blast destroyed four tons of chemical stock, mainly dimethylbenzene and cinnamene.

The district government of Songbei, where the plant is located, told Xinhua Monday that the fire brigade used 170 tons of water, some of which was drawn directly from a contingency water pool in the plant, to distinguish the fire after the explosion. 

"Pollution control was a top priority of the emergency response to the accident," said Liu Jixiang, a spokesman for the district government

He said the used water was contained in the plant area. An immediate sample test showed that phenol and cresylic chemical substances were in the water, and methanol in the air 1,000 meters downwind.

Environmental monitoring on the second day suggested benzene, alkane and alkene pollutants in the water, but no chemical pollutants in the air.

Contaminated water and earth in the plant were collected and sent for treatment at the Waste Treatment Center with the Municipal Bureau of Environmental Protection on April 8.

The blast caused no major environmental damage, said the bureau, adding that there were no drainage pipeline network beneath the plant, indicating no discharge of polluted water directly into the Songhua River.

The municipal government investigation into the accident found worker misconduct produced static electricity, which ignited a combustible chemical liquid in the storage tanks.

Investigators said the plant was ordered to suspend production three days before the accident, in which two workers were injured, due to the lack of permits from the environmental authorities.

The Songhua River suffered serious pollution last year when about 100 tons of pollutants containing benzene spilled into the waterway after a chemical plant explosion on Nov. 13 in Jilin Province. It was one of the worst river pollution incidents since the founding of new China in 1949.

Premier Wen Jiabao has ordered the launch of a series of projects to tackle industrial sources of pollution and to treat urban sewage, and for major pollution hazards to be effectively controlled and monitored.

Editor: Yan