Clare and North Tipperary county councils yesterday lifted their ban on public swimming in Lough Derg.
This follows the results of tests returned to North Tipperary County Council yesterday showing that the algae bloom in the lake has no toxicity.
The councils erected signs warning the public not to swim in the lake after two Labrador dogs died in the water last week.
The councils' fears were heightened because a third dog, a Doberman belonging to the same dog-owner, did not go for a swim in the Youghalarra area of Lough Derg with the two Labradors and remains healthy.
However, a spokesman for North Tipperary council confirmed yesterday that the tests have come back negative in relation to toxicity levels in the algae bloom.
He added that a postmortem carried out on one of the dogs found that he died from a "neuro-toxin of some strength". The spokesman said it has not been possible to identify the toxin. "The death of the two dogs is difficult to understand and we are still grappling with it. Linking it to the lake water is circumstantial."
The spokesman pointed out that the water quality of Lough Derg has improved in recent years, adding that staff from the Environmental Protection Agency have tested the water quality in recent days.
He confirmed that the ban has been lifted in the lake, but advised the public to exercise caution and ensure that any animals avoid scum-like substances on the lake shore.
The issuing of notices this week warning the public not to swim was the fifth year in a row this has happened on the Shannon's largest lake in response to a pollution scare.
However, Frank Lewis, of the Save Our Lough Derg group, said yesterday: "Not enough resources are being put to ensure that the quality of the water is good. Lough Derg is the jewel in the crown of the area and if you put in the resources, what price do we have to pay?"
