JOHANNESBURG — A group is warning that a lead poisoning crisis in northern Nigeria is still ongoing and affecting children, while government money has yet to be released.

Doctors Without Borders cautioned Thursday about the lead poisoning in rural Zamfara state, near Nigeria's border with Niger. The group says government money to clean up affected villages is still not available.

Without the funding, the group says more children will be exposed to the lead, which has been released from local gold mining in the villages.

The medical group also says the soil clean up hasn't started yet, although the country's rainy season is over.

The lead poisoning crisis began in 2010. At least 400 children have died since then, and thousands more continue to be exposed to dangerously high levels of lead.