LOUISVILLE, Ky. (WDRB) -- The beach at Patoka Lake in Indiana has reopened to swimmers. It was closed Thursday after high levels of E. coli were detected. 

Water test results returned on Friday show the E. coli levels back in the safe range. The Indiana Department of Natural Resources says recent visitors do not need to take any precautions. 

"No, not at all. They should not be worried. It may have been here when they were here, but I don't think they have anything to be concerned about being in the area," says Dana Reckelhoff, Interpretive Naturalist for the Department of Natural Resources.

Tests are usually performed weekly. "Usually on a Monday or beginning of the week, so we can get answers by the weekend when we're going to see an influx of people," Reckelhoff said.

A test this week showed the E. coli levels were too high for safe swimming. Higher levels of E. coli can happen in lakes, streams and creeks after heavy rains. Officials said Lake Patoka is a reservoir so its job is to hold water. E. coli bacteria are found in the environment, foods and intestines of people and animals. 

Although most strains of E. coli are harmless, some strains can cause illness. Some kinds of E. coli can cause diarrhea, while others cause urinary tract infections, respiratory illness pneumonia and other illnesses.

Click here for more information on E. coli.

Patoka Lake is in Crawford, Orange and Dubois Counties.

Thunder over Patoka Fireworks, scheduled for Saturday, will go on as scheduled.

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