A BBC investigation has revealed the level of toxic lead contamination around a cluster of villagers in Zamfara province in Northern Nigeria.

In the past four years 450 children have died from lead poisoning in the area. The lead is used to help extract gold from local mines.

Medical charity Medecins Sans Frontieres (MSF) has accused the Nigerian government of a slow and ineffective response to the contamination.

The government denies the accusation.

Tomi Oladipo reports.