An aid agency says that victims of a lead poisoning epidemic that killed at least 400 people in Nigeria's northwest are in need of long-term care.

The U.K.-based office of Doctors Without Borders said that the work it has been doing to treat the victims was only "a beginning" as it accepted the U.N.-backed Green Star Award for leadership in environmental emergencies Wednesday in Bern, Switzerland.

Emergency Manager Lauren Cooney called for new partners to get involved.

Doctors Without Borders treated more than 1,000 residents of Zamfara state since March 2010 in collaboration with other groups.

The epidemic is caused by the processing of gold ore in residential compounds, where people are exposed to toxic levels of lead found in the ore.