SEATTLE — Green Lake beaches in Seattle closed this week after high levels of toxic algae were detected in water samples.

A sample taken Monday found 7 micrograms per liter of microcystin, according to the Washington State Toxic Algae program. King County typically closes beaches for levels over 6 micrograms per liter.

Seattle Parks recommended people and pets avoid contact with the water or drink water from the lake until levels return to normal.

The lake will be resampled next week, according to Seattle Parks.

Bacteria monitoring at swimming areas has ended for the season, but algal toxic monitoring will continue through October, according to King County Water and Land Services.

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Blue-green algae is closely related to bacteria and can produce toxins that can potentially be deadly to people and pets. Warm weather, sunshine, and nutrients in the water can cause the algae to quickly reproduce, developing a bloom within days.