Officials with the Department of Water Management said Chicago's water supply continues to be safe to drink and use.
City officials re-tested the Lake Michigan water supply after Saturday's declaration that the Toledo, Ohio water supply from Lake Erie was unsafe to drink.
Officials said the water tests did not detect the presence of microcystin, a high toxic substance that has been found in Toledo.
The re-tested samples were taken to a lab in Indiana for overnight testing and Water Management spokesman Gary Litherland said the results came back with no detection of the microcystin, making the water safe to drink and use.
The mayor of Toledo, Ohio, said Sunday that it was still not safe for the 400,000 people in the area to drink tap water, but he said the level of toxins in the water supply appeared to be decreasing, NBC News reported.
“This is not over yet,” he said. Residents were told not to drink the water after tests at a treatment plant showed dangerous levels of microcystin, which can cause liver problems, diarrhea and vomiting.
The toxin apparently came from algae blooms in Lake Erie, authorities said.
Litherland said the department typically tests for the presence of blue green algae 2-3 times each week and will continue to monitor the situation in Toledo.