The Minnesota Department of Health is urging people living in areas affected by flooding to have their wells cleaned out, disinfected and tested before using the water again.
And it's not just wells that have come into direct contact with flood water. The agency says homeowners that have had flood water approach within 50 feet of a well may still be at risk.
Chris Elvrum, the Environmental Health Program Manager at the Department of Health, says flood waters often carry hazardous and toxic materials, including raw sewage, animal wastes, oil, gasoline, solvents and chemicals such as pesticides and fertilizer.
He says E.coli is common bacterial contaminant that can cause severe intestinal illnesses.
"We really recommend that if you have a bacteria positive or your well was flooded that you just avoid consuming it," said Elvrum.
That means waiting until a test comes back clean before drinking, cooking or brushing teeth with the water, he said.
The Minnesota Department of Health recommends hiring a professional well driller to clean out a contaminated well. A contractor can also disinfect the water or homeowners can do it themselves. The Department of Health has posted water disinfection directions on its web site.
The agency says it's also important to retest the well water using a certified testing lab.