(CNN) -- As residents of Toledo, Ohio, waited for word on when their water will be safe to drink, Mayor D. Michael Collins said Sunday morning that tests of the water supply were going to take longer than expected. He said results would likely be available Sunday afternoon but would not provide a specific timeline.
As many as 400,000 people were told not to consume, cook with or even boil the tap water, after a toxin called microcystis was found in the water supply late Friday. Collins told reporters the advisories will remain in effect until at least Sunday evening.
He said test results so far are "trending in a very positive direction." The tests are being done by the Environmental Protection Agency.
Toledo's drinking water comes from Lake Erie, where a harmful algae bloom that causes microcystis has been growing, according to a city spokeswoman.
Several locations around the city have been designated as distribution centers for potable water, where members of the Ohio National Guard, fire officials and other first responders are giving out safe water.
Lining up for water
Saturday morning, a line formed outside Walt Churchill's Market & Pharmacy in Perrysburg, Ohio, before the business even opened.
Toledo-area residents, desperate for clean water, bought all the bottled water inside, market co-owner Bob Carpenter said.
Then, hearing that a water tank truck full of about 8,000 gallons had set up outside the store, more people descended on the oasis with empty jugs they could fill for $1 a gallon.
About two-thirds of the Toledo area population is affected by the water warning. Ohio Gov. John Kasich issued a state of emergency for Fulton, Lucas and Wood counties. The potential contamination also affects four municipalities in Michigan, CNN affiliate WXYZ reported.
There are no reports of anyone getting sick from the water, officials said.
Harmful algal blooms
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 is crucial, because NOAA says it can't tell just from images if blooms are toxic or not.
Ingestion of the toxin can affect the liver and cause nausea, diarrhea, vomiting, and even acute liver failure, according to NOAA. But the Ohio state emergency management agency said it is safe for adults to shower and for everyone to wash their hands.