Public health officials in Quebec City sayresidents around Lac Saint-Charles should stay away from the water despite tests that show levels of cyanobacteriaare well within safe levels.

Tests conducted by Quebec's Environment Ministry found levels of blue-green algae in the lake are within acceptable norms, but biologists want to run more tests and have asked that residents in the area hold off from drinking or touching the water until Friday.

The lake, which supplies water to more than 250,000 residents in the provincial capital,was been flagged as potentially toxic after blue-green algae plants were found on the water's surface.

Health officials issued a warning Friday, instructing residents who use untreated water drawn directly from the lakenot todrink, cook, or brush their teeth with it.

Only people who live closeto the lake are affected by the advisory, said Jacques Perron, a city spokesman. There's no immediate danger to othersbecause the lake wateris funnelled through a filtration system that can eliminate cyanobacteria, the toxic component in blue-green algae, Perron said.

Health officials were informed about the algaeafter a resident found a plant floating ina bay on Oct. 8.

Algae affects several communities

The advisory in Quebec is the latest water scare to trickle fromblue-green algae overgrowth.

Public health officials in the Baie Sauvage region, about 70 kilometres northeast of Sherbrooke, issued a water warning in early October forresidents living near the Grand Lac St-François.

Residents in the Lambton, St-Romain and Ste-Praxède municipalities were told Oct. 11 to avoid using or touching the lake water because of high levels of cyanobacteria.

In the Eastern Townships, about 5,000 residents in Hatley Township, North Hatley, Waterville and Ayer's Cliff have been living under a water ban since Sept. 22, when health officials determined blue-green algae in Lake Massawippi had reached potentially toxic levels.

The results from long-term tests on the lake won't be available until the end of October, according to officials with the Quebec Environment Ministry.

Elsewhere in the province, residents in Fossambault-sur-le-Lac and Saint-Joseph, two towns north of Quebec City, are living with an indefinite ban on drinking water drawn from Lac Saint-Joseph, which is overrun with algae.

More than 50 Quebec lakes in total have suffered from blue-green algae overgrowth this past summer, according to environmental groups. Activists haveurged the province to act more aggressively to protect lakes that provide drinking water.

Meanwhile, residents around the Massawippi and Saint-Joseph lakes have created local associations that will come up with community measures to contain the algae's growth,by limiting the use of phosphate-based fertilizers near the waterfront.