"The result would be terrible if incidents happened in these factories," Zhou told reporters.

A national investigation on these factories was carried out before the end of January.

The problems have been caused by China's rapid economic development, which has sometimes been at the expense of environmental protection, Zhou said.

"It is impossible to solve these problems overnight," he said.

His predecessor, Xie Zhenhua, resigned after the Songhua incident.

New guidelines have since been drawn up that clearly specifies the objectives, tasks and policy measures for environmental protection in the future.

The ability to protect the environment will become a vital measure as to whether officials at various levels are qualified or not in their roles, the guidelines state.

In 2005, nearly 30,000 environmental infringement cases were investigated and sanctioned. Among them, 2,609 enterprises were suppressed or closed down, and more than 300 people punished.

Top Chinese leaders, including Premier Wen Jiabao, have promised at the annual session that China is devoted to building an energy-saving and environment-friendly society in the coming five years and beyond.

The previous ignorance in environmental protection has made China pay a lot in the past several years. In the first four years of the State's 10th Five-Year Plan period (2001-05), China invested a total of 600.6 billion yuan (US$72.3 billion) in pollution prevention and control.