A federal judge in South Dakota today ordered the U.S. Army Corps of Engineers not to raise the level of a reservoir along the Missouri River before removing human skeletal remains scattered on the surface of a former Indian burial site.

But U.S. District Judge Lawrence L. Piersol ruled that after the bones on the surface are removed, possibly within days, the engineers may flood Lake Francis Case, about 100 miles southwest of Sioux Falls, and cover up more skeletal remains and coffins that were partially unearthed when the corps lowered the level of the reservoir last month.

He urged the corps to negotiate with the members of the Yankton Sioux Tribe in a "culturally sensitive way" to reach an agreement on a schedule for flooding the lake.

Tribal leaders, who sued the corps to prevent it from raising the lake level until they completed mapping and excavation of the burial site, said the ruling was a partial victory because it set a precedent for the protection of sacred Indian sites.

Tribal spokeswoman Tessa Lehto said corps officials and a tribal archaeologist will begin mapping the grave site Thursday so that when the reservoir level drops next fall the tribe can begin exhuming all of the bodies and rebury them according to tribal customs.