'Catastrophic failure:' 21K fish found dead at UC Davis

A total of 21,000 fish being used for research at the University of California Davis have died.

University officials called it a "catastrophic failure."

The deaths occurred at the university's center for aquatic biology and aquaculture.

According to the university, the fish were exposed to chlorine.

School officials are investigating what went wrong.

The fish were being used for several different research purposes, including an investigation into environmental stressors on fish species.