Water testing on a stream in Putaruru has not yet identified a likely cause for the recent deaths of hundreds of koura (freshwater crayfish).

Waikato Regional Council's incident response team first attended the Oraka Stream after a local fisherman reported seeing the dead koura during a visit to the stream on December 20.

Council staff returned to the stream for five consecutive days to gather water samples and carry out an extensive search of the area, as well as to speak with a number of upstream businesses as part of their inquiries, says incident response team leader Derek Hartley.

'It appears a single acute event has killed the koura. However, the good news is that other aquatic life has been seemingly unaffected by it.

'The results of testing on water samples collected over five days last week have been analysed by our scientists, and there's nothing that clearly identifies a likely cause of the deaths.”

While it's good news that there's been no further deaths of koura reported, Derek says the regional council will continuing to eliminate potential causes as part of its ongoing investigation.

Derek encourages anyone with information on the possible cause of the koura deaths to contact the Waikato Regional Council on 0800 800 401.