Lake Anza in Berkeley has been closed for swimming due to a bloom of toxic blue-green algae, the East Bay Regional Park District announced today.
The lake, located in Tilden Regional Park in the hills east of Berkeley, will remained closed pending further water-quality tests.
Lake Anza joins three other lakes in the region that have all been afflicted with toxic algae.
In July, park officials put a stop to swimming in Lake Temescal in Oakland due to an algae bloom. Quarry Lakes in Fremont was closed about two months before that for the same reason.
Though swimming is not allowed in Lake Chabot in Castro Valley, officials have warned of toxic algae there as well.
Park officials said toxic algae is a rare but natural phenomenon, most likely caused by the drought.
Toxic algae can cause skin irritations and gastro-intestinal problems in humans and can be fatal to dogs.