Lead poisoning from illegal gold mining in the Nigerian state of Zamfara has killed at least 400 children in the past six months, it has been revealed.

The deaths have been attributed to villagers dumping the by-product of crushed gold ore rocks.

A team from the UN Environment Programme and the Office for the Coordination of Humanitarian Affairs said thousands of people are at risk after analysing soil and water samples from five villages in Zamfara.

The sudden increase in lead-related illnesses and deaths emerged early 2010 in two districts of Zamfara, due to attempts by locals to extract gold from lead-contaminated soils in and around their houses and compounds, reports telegraph.co.uk.

Lead poisoning causes irreparable damage to neurological systems, and can lead to reduced IQ, behavioural disorders and loss of control of muscles. It can also affect foetal development.