DETROIT (WWJ) – Officials say the first round of tests came back clear while a big chunk of the city of Detroit remains under a boil water advisory.

The Michigan Department of Environmental Quality said in a media release, Thursday afternoon, that while the results of the tests by the Great Lakes Water Authority (GLWA) “are a sign that there is nothing wrong with the water,” the advisory will remain in effect at least until noon on Friday, to be safe. (Initially, it was expected to be lifted as early as Thursday evening).

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That depends, however on second round of test results to be returned Friday, officials said. Upon a second clear result, the GLWA will recommend that the boil water advisory be lifted.

Sheryl Porter, Chief Executive Officer of the GLWA, is optimistic.

“In the first round of samples, which we communicated, we had clear results,” she reiterated, in an interview with WWJ’s Stephanie Davis. “I fully expect to have the same conclusion tomorrow.”

The areas affected by the boil water advisory are McNichols south to the Detroit River, and Linwood east to Conner. This includes downtown Detroit and the campus of Wayne State University, along with all of Highland Park and Hamtramck.

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Meantime, dozens of Detroit schools were closed as a result, and numerous local business have been affected.

Grace Forrest, a barista at Roasting Plant in Campus Martius, said they’re using bottled water to wash the dishes and aren’t able to serve iced coffee.

“We did have to bring in water,” she told WWJ’s Mike Campbell, Thursday morning. “A lot, and I’m sure more’s coming.”

Recommendations are to bring all water to a boil for one minute and let it cool before using, or to use bottled water. Boiled or bottled water should be used for drinking, making ice, brushing teeth, washing dishes, and food preparation until further notice. Boiling kills bacteria and other organisms in the water.

While details haven’t been released, officials said the issue was a result of a “failure at Great Lakes Water Authority facility” Tuesday, causing low water pressure.

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Any residents or businesses without water service in the defined area is urged to contact the Detroit Water and Sewerage Department’s emergency line at 313-267-7401.