Tap water remained off-limits for nearly half a million people in northwestern Ohio early Monday after testing showed continued cause for concern. It was the third day of the crisis, which erupted after the city of Toledo, Ohio, said Saturday a toxin had been detected in the water supply and warned residents not to use the tap for drinking, bathing and even cooking. Police were called in to help order as residents emptied store shelves of water, and water distribution sites were opened throughout the area. Governor John Kasich declared a state of emergency, and the Ohio National Guard began providing tens of thousands of gallons of water.

Toledo Mayor D. Michael Collins said early Monday that while tests continued to show a positive trend, they "do not convince us of safety," NBC station WNWO reported. He said the advisory remains in effect and more tests will be carried out, with “satisfactory” results in the majority of areas but two "spots of concern" remain. The advisory was put in place after tests at a treatment plant showed above-standard readings for microsystin, which can cause liver problems, diarrhea and vomiting. Researchers said that sewage from treatment plants and fertilizer from farms streamed into the lake, triggering an algae bloom near an intake valve that sends water to Toledo and more than a dozen surrounding communities.

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Mayor Collins: I've instructed our people to go resample because I will not take any chances with community's safety &- NBC 24 (@nbc24wnwo) August 4, 2014

Mayor Collins: US and Ohio EPA numbers are all satisfactory, Toledo tests do not convince us of safety -NBC 24 (@nbc24wnwo) August 4, 2014

- Cassandra Vinograd