The Nairobi-based UN Environment Programme (UNEP), which sent a team to China's northeast to investigate damage to the Songhua River and surrounding areas caused by the November spill, said Chinese authorities had reacted too slowly in informing the public of the dangers.

"It is clear that, during the initial response phase, government communication and information sharing with the general public was not adequate enough to ensure appropriate responses of the affected population," it said in its report on the incident.

UNEP suggested that China work with it to implement an emergency response plan for local authorities who did not disclose that the river had been contaminated until 10 days after the spill was caused by a massive November 13 explosion at a benzene factory.

"Further investigations are needed to clarify whether existing early warning systems and contingency plans were sufficient," it said. "Furthermore, an analysis of the internal risk management practices of industry should be undertaken ... to assess the state of preparedness and identify capacities and legislation or regulations required to minimize the risks.

"UNEP is ready to assist the government of China in this regard," it said, adding that China and Russia cooperate on emergency response and disaster contingency plans in addition to sharing chemical analyses, including air quality samples, from areas affected by the spill.

Senior Chinese officials and the parent company of PetroChina, the firm whose benzene plant explosion caused the spill, have apologized for the environmental crisis which shut down water supplies for up to four million people in Harbin, one of China's largest cities, for five days.

The 80-kilometer-long (50-mile) slick of highly toxic and carcinogenic benzene flowed through Harbin along the icy, 1,900-kilometer (1,200-mile) Songhua, which provides the city and surrounding population of nine million with much of its water as well as more than a million across the border in Russia's far eastern Khabarovsk region.

Fifty tonnes of chemicals, mostly benzene and nitrobenzene, are believed to have been absorbed in the river bed and deposited along the banks above Harbin, while the other 50 tonnes from the explosion were thought to have passed through the city, posing risks for Chinese further downstream and people in Russia.

According to China, the benzene pollution levels at some points on the river exceeded national safety levels by a factor of 103. Benzene exposure at high levels can be fatal even in small doses.

UNEP said the spill was "of major transboundary and international significance" and as such should be reviewed by independent scientists using established and neutral laboratories.

"It is a common practice that in transboundary incidents, sampling and analysis are undertaken by all countries involved and affected as well as by an independent internationally recognized laboratory," it said.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.