Oakland’s Lake Temescal closed due to toxic algae

Lake Temescal in Oakland was closed to swimmers and dogs after an outbreak of toxic algae was detected in the water, park officials said.

It’s unclear what caused the toxic blue-green algae, also known as cyanobacteria, to bloom, said Hal MacLean, a water management supervisor with the East Bay Regional Park District.

The lake was closed to swimmers Tuesday, and dog owners were advised to keep their pets out of the water.

Casey Gallagher of Oakland fishes Lake Temescal in Oakland, California on Sat. Sept. 24, 2016, as temperatures soar throughout the Bay Area. Casey Gallagher of Oakland fishes Lake Temescal in Oakland, California on Sat. Sept. 24, 2016, as temperatures soar throughout the Bay Area. Photo: Michael Macor, The Chronicle Buy photo Photo: Michael Macor, The Chronicle Image 1 of / 4 Caption Close Oakland’s Lake Temescal closed due to toxic algae 1 / 4 Back to Gallery

Lake Temescal, a reservoir in the Oakland hills, is one of several lakes closed in the East Bay Regional Park District. Quarry Lakes in Fremont are also no longer open to swimmers due to the toxins.

It’s unclear when Lake Temescal will be reopened to swimmers, MacLean said.

Blue-green algae was also found at Lake Del Valle in Livermore, Lake Chabot in Castro Valley, Lake Anza in Berkeley and Shadow Cliffs in Pleasanton. However, officials said no toxins were present.

Nonetheless, park officials advised visitors to keep their dogs away from the water.

The parks remain open for fishing, picnicking and hiking.

Lake Temescal was closed several times last summer because of the toxic blue-green algae bloom.

Sarah Ravani is a San Francisco Chronicle staff writer. Email: sravani@sfchronicle.com Twitter: @SarRavani