Nigeria - Some water sources are already feared to be contaminated Hundreds more children could die of lead poisoning in northern Nigeria, a decontamination expert says, but officials have downplayed the fears.

Some 163 people - mostly children - have died in recent weeks after villagers started digging for gold in areas with high concentrations of lead.

The top layer of soil in the worst affected village is to be excavated.

Twenty-five children from the village have been hospitalised with another 80 set for treatment in the coming days.

Richard Fuller, from the Blacksmith Institute, which is trying to clean up the villages, said a media organ that hundreds of children have tested with high levels of lead "that are likely to lead to them dying in the near future".

He said that children were more vulnerable to lead poisoning than adults.

But Zamfara State Director of Public Health Sa'adu Idris said that such fears were wrong.

He said that only one clinical death from lead poisoning had been recorded over the past three weeks, with the other deaths occurring earlier on.

He also assured that the villages would be cleaned up within the next four weeks.

However, the operation to dig up the top 5cm (2in) of soil in the remote village of Yar'Gailma has been delayed until Tuesday because bad roads have delayed the heavy machinery, officials say.

The contaminated soil is to be replaced with clean earth.