A?man has been arrested for dumping waste liquid containing solvents into a city river and causing pollution in suburban Qingpu District, police said yesterday.

The suspect, surnamed Gu, was a legal representative of a trade company in the district, police said.

District police and environmental authorities were alerted late on April 11 after residents reported a pungent smell in the Dianpu River. Witnesses said "something like oil or paint" was floating on the river surface.

Authorities traced the source of the pollution to the Shanghai Puteng Trade Co Ltd along the riverside of the Dianpu River.

Police also listed Gu, who had fled, as a wanted person. Gu gave himself up on April 16, officers said.

He told police he dumped waste fuel, which had been stored for a long time, into an open area after first diluting the liquid.

But the waste, containing organic solvents such as limonene, flowed into drains and through the sewage system entered the river, environmental officials said.

The district environmental authority said the waste was removed the following morning and never threatened residents' tap water.

Environmental officials conducted checks on the river over the following three days and found the pollution decreased over the period.

The city's environmental authorities have increased penalties for water pollution, with those responsible facing fines of up to 1 million yuan (US$153,916).