But the official also warned that China will find it near impossible to avoid serious accidents even after a chemical spill in November galvanized national concern about the ecological damage that has accompanied China's industrial boom.

"Due to the geographic distribution of environmental threats and structural environmental risks, for some time to come high-risk conditions for sudden environmental incidents will continue," the official said.

The spill in the Songhua River in far northeast China came after a blast at a chemical plant near its banks poured 100 tonnes of cancer-causing benzene into the river.

It led to the shutting of water taps in cities and towns in Heilongjiang province, as well as emergency measures in Russia, where the river flows.

"The Songhua River incident was a major challenge and a big test," SEPA vice director Pan Yue was quoted as saying on Tuesday on the watchdog's Web site, www.zhb.gov.cn.

"We paid a dear price, but we also gained some new wisdom, new ways of thinking and new motivation."

Pan named 11 companies for failing to prevent pollution at their factories, including riverside smelters and chemical plants, in the administration's latest push to prevent more environmental crises.

The 11 companies, as well as 10 factories and infrastructure projects under construction, had to clean up their acts quickly or face fines and orders to stop production, he said.

SEPA received official reports of 45 other pollution accidents in the two and a half months after the Songhua spill, and nine were caused by factories illegally expelling pollutants, the unnamed official told the People's Daily.

Factories "only concern themselves with their immediate interests", ignoring pollution hazards, the official said. He cited a smelter in southern China's Guangdong province that dumped poisonous chemicals into the Beijing River in mid-December.

The government's response to the Songhua River spill has been widely criticised, leading to the early December resignation of former SEPA head Xie Zhenhua.

Law suits have also been filed, mostly aimed at officials in Jilin province where the chemical plant that released the benzene is located.

But SEPA officials said at the time they received no reports from Jilin province officials for three days after the blast.

The Chinese government has promised to improve China's environmental safeguards and spent billions of yuan on cleaning up the country's rivers.

But the state-controlled Workers Daily reported on Tuesday that 4.55 billion yuan (US$564 million) spent over 14 years on cleaning up the Dianchi Lake in southwest China's Yunnan province has done little to improve water quality.