Park officials have closed Seattle's Green Lake to wading, swimming and activities like sail boating due to a toxic algae bloom.
The lake is closed to these activities due to the presence of a cyanobacterial toxin that exceeds the Department of Health's guidelines, said Seattle Parks and Recreation Acting Superintendent Christopher Williams.
At least one person was spotted swimming in Green Lake Wednesday morning, more than 12 hours after signs were posted as a warning.
Parks officials also said dog owners should avoid allowing dogs to drink from the lake.
The lake is open to fishing and boating - activities where users are unlikely to ingest the water.
Officials say the closure will be in effect until the algae bloom completes its life cycle, which could likely be weeks or months, depending on the fall weather affects the algae bloom. Dry weather typically continues the bloom.
For more information on cyanobacteria, visit King County's Major Lakes Monitoring webpage or the Washington Department of Health toxic algae website.