At least 10 trucks that had carried coal to the plant were damaged. Some of them were from Henan Province and the Ningxia Hui Autonomous Region.

Baoji Mayor Dai Zhengshe has been appointed as head of a newly-established pollution control team. He said he was willing to settle the villagers' relocations and medical issues through dialogue.

More than 200 officials have begun hearing the villagers' woes since Monday morning.

Residents living within a radius of 500 metres from the plant were supposed to have been relocated by this year according to a deal reached between the plant and Fengxiang county government before the plant opened in 2006.

Relocation, however, is running far behind the government's schedule and only 156 of the 581 families have moved to new homes.

The government of Fengxiang county began building new homes last Thursday for the remaining 425 families.

The local environment watchdog has blamed the smelter for the lead poisoning.

'Lead content in the air along the main routes near the plant is 6.3 times that of monitoring sites 350 metres from the roads,' said Han Qinyou, head of the Baoji Municipal Environmental Protection Monitoring Station.

But the official said laboratory tests on samples also showed 'ground and surface water, soil and the smelter's waste discharge had all met national standards'.