Millions of dead sardines filled the northern part of Redondo Beach's King Harbor on March 8, 2011.
Researchers say the millions of sardines that were found floating dead in a Southern California marina this week tested positive for a powerful neurotoxin.
University of Southern California biologist David Caron said Friday that high levels of domoic acid were found in the fish scooped from the Redondo Beach marina.
He said critically low oxygen levels in the water caused the sardines to suffocate, but it's possible the toxin distressed them off the coastline and caused them to crowd into the marina.
Domoic acid is often found in the stomach of fish that have been feeding on plankton during toxic algae blooms. Caron's lab is working to determine if the poisoning was caused by a toxic algae bloom spotted off Redondo Beach on Wednesday.