The Minnesota Department of Health says five northeastern beaches have dangerously high levels of E. coli bacteria.
Contact with E. coli in the water could lead to gastrointestinal illnesses, or skin and eye infections.
The department has posted advisories against contact with water at two beaches in Two Harbors and three beaches in Duluth. Health department program manager Amy Westbrook said it's early in the season to be seeing such high levels.
"Most likely it's really affected by the rain and heavy winds that we're having," Westbrook said. "We have been having a lot of rain the last couple of days, which shouldn't be surprising to us that we're seeing more postings than we would normally at this time of year."
Westbrook said the rain probably caused runoff that stirred up sediment, releasing E coli into waterways.
"What researchers at UMD have found there's naturally occurring E. coli in the sediment," she said. "So it's not to say that we're identifying that there's a certain amount of pathogenic E. coli, it's just E coli as an indicator of other bacteria."
Westbrook said the beaches are due to be tested soon and likely won't be under advisories for long.