Wildlife officials say they've confirmed that an ongoing fish kill at Roosevelt Lake is being caused by golden algae.
Biologists are monitoring the situation at the lake northeast of Phoenix. Most of the dead fish appear to be large gizzard shad. The fish are particularly affected by the toxin put off by the algae.
Arizona Game and Fish officials say 30 to 40 dead and decaying fish are regularly being found around the lake.
Biologists don't know what causes golden algae to produce toxins that kill fish. Biologists say if the toxin levels continue to increase other species of fish could also be affected.
A golden algae bloom killed fish along a 20 mile stretch of the Salt River in July. The toxin doesn't harm people.