( CNN ) -- A tap water ban affecting hundreds of thousands of people in Ohio was lifted Monday after tests in affected neighborhoods returned `` nondetectable '' levels of a algae-related toxin , Toledo Mayor D. Michael Collins said . `` Our water is safe , '' Collins said . `` The families can return to normal life . '' Residents and businesses that did not use their water at all -- not even for showering or washing hands , both of which were allowed under the ban -- will need to run their water first to help flush their systems , Collins said , but `` if you 've been using water all along , just go on with life . '' Collins said the city would provide details later Monday about flushing systems . Residents of Ohio 's fourth-largest city were told to avoid using their tap water all weekend after the state and federal Environmental Protection Agency showed high toxin levels in the East Toledo and Point Place neighborhoods , Collins said earlier Monday . Instead of isolating the two neighborhoods , Collins kept the ban on drinking or using tap water in the entire city until additional retests were completed . He declined to provide specifics on the names of neighborhoods in question and how high the toxin levels were . As many as 400,000 people were told not to consume , cook with or boil the tap water after a toxin called microcystin was found Friday in the water supply . Toledo 's drinking water comes from Lake Erie , where a harmful algae bloom that causes microcystin has been growing . The city set up distribution centers for potable water , where members of the Ohio National Guard , fire officials and other first responders were giving out safe water . About 350 Ohio National Guardsmen were activated by Ohio Gov . John Kasich , according to a U.S. Defense Department official , adding that they set up three reverse osmosis water purification unit sites at two high schools and a police facility . The guardsmen also delivered ready-to-eat meals , the official said . Lining up for water . About two-thirds of the Toledo area was affected by the water warning . Kasich issued a state of emergency for Fulton , Lucas and Wood counties . The potential contamination also affected four municipalities in Michigan , CNN affiliate WXYZ-TV in Detroit reported . There were no reports of anyone getting sick from the water , officials said . When certain conditions are present , such as high nutrient or light levels , algae can reproduce rapidly , forming a dense population known as a `` bloom , '' according to the National Oceanic and Atmospheric Administration . Testing was crucial because NOAA says it ca n't determine just from images whether blooms are toxic . Ingestion of the toxin can affect the liver and cause nausea , diarrhea , vomiting and acute liver failure , according to NOAA . But the Ohio Emergency Management Agency said it was safe for adults to shower and for everyone to wash their hands . CNN 's Eliott C. McLaughlin , David Shortell , Ryan Sloane , Barbara Starr , Marisa Marcellino , Donovan Long and Kristina Sgueglia contributed to this report .
NEW : `` The families can return to normal life , '' Toledo mayor says of water ban . Tests showed high levels of toxins in two Toledo neighborhoods . Microcystin , a toxin caused by algae blooms , found in the water system .