OAKLAND — The popular Lake Temescal is closed to swimming again because of a bloom of toxic blue-green algae just as the swim season heats up.

East Bay Regional Park District officials said Tuesday that the lake in the Temescal Regional Recreation Area near the Caldecott Tunnel will be closed until tests show the toxic algae has decreased to safe levels. Lake Temescal, which attracts many families with children, was closed last year during much of the swim season.

The algae, also called cyanobacteria, is a naturally occurring bacteria that can turn toxic in water, causing nausea, vomiting and gastrointestinal problems in people. The toxins can kill dogs that swallow contaminated water.

Related Articles Toxic algae troubles many California lakes and waterways This is the second regional park swim lake to be closed this year due to blue-green algae. The swim area at Quarry Lakes Regional Recreation Area in Fremont was closed Feb. 8 because of the bacteria after it reopened in November from another closure, said Hal MacLean, the park district’s manager of water quality.

Related Articles Toxic algae troubles many California lakes and waterways

Why does water suddenly taste bad in parts of the East Bay? Unchlorinated swim lakes that remain open include Del Valle Reservoir in Livermore, Shadow Cliffs in Pleasanton, and Lake Anza in Tilden Regional Park in Berkeley.

The park district maintains a website section for the public to check on water quality and closures at its swim beaches.

As of Friday, three swim areas were closed in California due to toxic algae, according to the state Water Resources Control Board, but the number is expected to increase because the algae thrives in warm stagnant water.