Doctors Without Borders (MSF) on Thursday urged Nigeria to release funds promised to clean up an area where lead poison killed hundreds of children, warning that further delays could be "disastrous."
The lead poisoning crisis in northwest Zamfara state was called the worst such epidemic "in modern history" by Human Rights Watch, with an official death toll saying 400 children were killed and thousands more affected.
In a new report, MSF called on Nigeria to release the pledged clean up funds before the end of November to ensure the contaminated soil was cleared before the next rainy season starts in April.
Remediation, or the process of removing the toxic soil, cannot be carried out during the rainy season.
MSF said begining medical treatment before the remediation was complete would be "useless" because those treated would still face a high risk of re-infection.
According to the humanitarian group, Nigeria's federal government in May committed to providing 850 million naira ($5.4 million, 4.2 million euros), but has so far failed to deliver.
"If the funds are not released now, MSF's chance to treat the lead poisoned children of Bagega (in Zamfara state) will be drastically reduced," the report said.
Lead was dispersed in the several Zamfara areas by the processing of ore for gold extraction using unsafe mining techniques. Illicit gold mining is more lucrative than agriculture for the impoverished farming communities.
The extent of the poisoning in the area began to come to light in 2010.
Local communities had initially largely concealed or denied the fatalities and illnesses from lead poisoning for fear that authorities would ban their mining activities, MSF said previously.
Remediation has been carried out in some areas, but in the hardest hit village of Bagega and the surrounding communities "hundreds of children... continue to needlessly suffer the effects of lead poisoning."
If the clean up is not complete by April, it "could have disastrous consequences for the community," MSF said.
Explore further: Nigeria lead poisoning 'worst in modern history': HRW