The Ministry for Primary Industries has confirmed one of its vehicles was involved in an accident near Ninety Mile Beach that left an 11-year-old boy critically injured.
A rescue helicopter was sent and emergency services were at the scene, on Te Paki Stream Road.
Police were alerted about 1.30pm.
The road would stay closed until the serious crash unit completed its scene examination.
The Ministry said it was offering support to the fisheries officer involved.
In addition to the police investigation, the Ministry said it would be doing its own review of what happened.