Waikato Regional Council's oil spill response team is reacting to reports of a diesel spill at Kawhia wharf.
Regional on-scene commander Adam Munro said there were reports of diesel on shore near the wharf as a result of the spill.
Staff were investigating exactly what had happened, how far the spill had spread and what impact it had had.
"We are also looking at any spill containment and clean up that may be required," Mr Munro said.
"We urge people to avoid the area while we investigate and to stay away from any diesel they come across."