Biosecurity Minister Jim Anderton has confirmed that there is no evidence of live didymo in the river samples from the central North Island.
The Tuwharetoa Maori Trust Board, which had restricted road access to the Tongariro River and surrounding area as a precaution, has now re-opened the area.
Similarly, Genesis Energy has recommenced power generation on the Western and Eastern diversions of the Tokaanu Power Station.
Advocates will continue to be out on rivers advising river users to check, clean and dry.
This episode is a wake-up call to us all about who owns the responsibility for the spread of didymo. The answer is every single New Zealander, as well as those who visit New Zealand to share our pristine environment with us, Jim Anderton said.