By Peter Greste
BBC News, East Africa correspondent
Southern Sudan is rich in oil
A German aid agency has accused an oil consortium in southern Sudan of contaminating water supplies, affecting at least 300,000 people in Unity State.
The group, Sign of Hope, said tests found life-threatening metals in wells near two major oil fields.
It said it had passed the findings to the government and the consortium.
The White Nile Petroleum Operating Company says protecting water quality is a priority and it has built a water treatment plant for the community.
But it could not be reached to comment directly on the allegations.
Sign of Hope said it did the tests by Mala and Thar Jath oil fields after local villagers complained the water tasted salty and had been making them sick.
The agency's vice-chairman said they were startled by what they found.
"The chemical composition of water samples we have taken from oil well drilling pits is nearly the same as we found in the contaminated water boreholes the people are using for drinking water supply," Klaus Stieglitz said.
If the local community cannot find alternatives, Mr Stieglitz said the effects on their health could be devastating.
He said that the water treatment plant was a help, but not enough and would not solve the wider environmental problems.
Mr Stieglitz also feared there could be environmental implications for the nearby Sudd swamp, one of the world's largest wetlands formed by the White Nile - although no tests had been carried out on its waters.