"I'd heard that he'd died at home yesterday. We've heard that he hanged himself," a senior city official said.

Other city officials confirmed that he had been found dead at home, but would provide no other details. Two others said he was not under investigation of any kind.

Wang had been quoted as saying that the accident would not cause widespread pollution. In fact 100 tonnes of cancer-causing benzene compounds spilt into the Songhua river which provides drinking water for the 9 million people of the city of Harbin. Tap water supplies had to be shut off for nearly a week.

Official media have reported that Beijing has promised harsh punishment for anyone guilty of misconduct over the incident.

Investigators would also look into attempts to cover up the gravity of the incident, Xinhua news agency said.

The slick is now winding its way northeast towards the Russian Siberian city of Khabarovsk, through areas populated by millions of Chinese, but the cold winter is freezing the Songhua, slowing its movement.

Chinese Premier Wen Jiabao said China was working with Russia to deal with the slick.

"We are taking effective measures to remove the pollution from this river and secure clean drinking water," Wen told a news conference on a visit to the Slovak capital Bratislava.

"We have provided information to the Russian side and we have provided the necessary technical assistance and equipment."

DAM PROPOSAL

Heilongjiang Province is considering a proposal raised by the Russian side to build a temporary dam at the mouth of the shallow Fuyuan waterway, to prevent contamination of Khabarovsk's water source, Xinhua said, citing local Chinese water officials.

The Fuyuan flows into the confluence of the Heilong and Wusuli rivers, both of which form the Russian-Chinese border in China's northeastern-most corner.

Beijing had earlier apologised to Moscow for the pollution, and for the delay in sounding the alarm.

An official at Jilin city hall confirmed Wang's death.

"City officials are meeting to deal with the issue and some are going to the scene to conduct investigations", he said, adding that by "the scene" he meant Wang's home.

"After the investigation, we might release the results," he said, declining to give more details or his name.

State media have so far not mentioned Wang's death.

Chinese media is all, to varying degrees, owned by the state. On sensitive issues like corruption and disasters, newspapers and other outlets are only allowed to report the official line put out by the central Xinhua news agency.

Xinhua said on Wednesday that the slick had reached the outskirts of Jiamusi city, near the Russian border.

The report said residents had begun leaving their homes and stocking up on drinking water although the pollution had yet to be detected in the city itself.

Last week, Xie Zhenhua, chief of the State Environmental Protection Administration, resigned because of its failure to face up to the crisis, state media said.