The United Nations says some 400 children in northern Nigeria have died since March from lead poisoning linked to illegal mining by residents for gold and thousands more remain at risk. Most victims are under age five. A spokeswoman of the UN Office for the Coordination of Humanitarian Affairs, Elisabeth Byrs said lead pollution and intoxication crisis in Zamfara state is far from over and an urgent and coordinated response is needed. A UN assessment mission, acting at the request of the Nigerian government, found that water supplies in four out of five villages it visited were contaminated by high levels of lead.