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After a summer of poisonous algal blooms, Utah Lake is once again fighting contamination in its waters: This time, it's E. coli.

The Utah Department of Environmental Quality (DEQ) advises people to stay out of the lake's northern end — the area surrounding Lindon Marina — after test results showed "high levels" of the bacteria, according to a news release from the agency. Swimming in or ingesting the water can cause diarrhea, urinary tract infections and intestinal distress; in severe cases, they can be fatal.

E. coli comes from human and animal feces, the release states, and can build in waterways with faulty sewer systems, livestock in the area, large concentrations of waterfowl and stormwater runoff. The pollution risk, though, is higher after rainstorms because precipitation comes off sidewalks, farms and lawns, carrying contaminants into rivers and lakes.

It's unclear what brought the E. coli to Utah Lake.

"There was not any event that could pinpoint the cause of it," said Donna Spangler, DEQ spokeswoman.

The DEQ monitors the lake monthly from May through October, looking for bacteria. Samples collected from Lindon Marina on Friday show levels that exceeded the health threshold, though Spangler was unsure by how much. Additional samples collected Monday, the release states, showed low levels at American Fork Harbor and Utah Lake State Park Harbor, but E. coli contamination on the dike on the northern edge of Lindon Marina remained high.

The agency advises people to wash their hands after handling fish or touching the water there.

The lake — and several others in the state, including Scofield Reservoir and Big East Lakesuffered from algal blooms this summer, starting with a miles-long slick in mid-July. Though it is unrelated to the E. coli, the toxic cyanobacteria in algae also temporarily closed the waterways. Those growths are caused by high levels of nutrients, warm temperatures, calm flows and heavy sunlight.

As of Sept. 19, Utah Lake remained under a caution advisory due to the blooms.

ctanner@sltrib.com Twitter: @CourtneyLTanner