Crow tribal officials are warning residents that reservation water supplies are tainted.
"We still have contaminated water," said Jared Stewart, a tribal information officer.
People need to avoid creeks and riverbanks after floodwaters overwhelmed the water treatment plant, he said, and a boil order remains in place.
A donation site is set up at Little Bighorn College and water, canned goods, dry goods and toiletries are the most-needed items.
After a meeting this morning, Stewart said, officials said that though a flood in 1978 was devastating, the water levels of this flood are actually worse.
Some areas have been hit harder by this flood, but improvements made to bridges and infrastructure are mitigating the damage, he said.