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.
—By Cassandra Vinograd, NBC News