TOLEDO, Ohio (AP) _ The Toledo area’s local health department says no signs of illness were reported after a small amount of the northwest Ohio city’s water supply didn’t get a full chlorine treatment in mid-March.

WTOL-TV ( ) reports residents weren’t told about the problem until mid-May, and some raised concerns.

The Toledo-Lucas County Health Department says the chlorine is used to kill parasites and viruses. Health officials looked through reports to see if anyone might have become sick from consuming the untreated water, but they found no sign of that.

The city says it corrected the problem using an alternative treatment. Officials say the water is safe to drink.

The concerns come less than a year after algae in Lake Erie contaminated drinking water for 400,000 people in Toledo and southeastern Michigan.