The mystery around the unexplained deaths of hundreds of koura (freshwater crayfish) in a Putaruru stream is continuing to be investigated.
Waikato Regional Council staff first went to Oraka Stream, near Galway St, 10 days ago after a fisherman reported seeing the dead koura.
But testing of water samples, an extensive search of the area and inquiries with businesses upstream have failed to identify a likely cause of the mysterious deaths.
Team leader Derek Hartley says it appears a single acute event has killed the koura.
"The good news is that other aquatic life has been seemingly unaffected by it."
He says the good news is that other aquatic life has been seemingly unaffected and there have been no further deaths of koura.
"We're continuing this week to eliminate potential causes as part of our ongoing investigation," he said.