Fire has broken out inside a Ballance Fertiliser plant near Hastings.
Twelve fire engines are in attendance fighting the contained blaze in a building 100 metres long by 50m wide on State Highway 50A.
Wellington central fire acting communications manager Craig Dally said it was too early yet to say how much damage had been done to the building.
Emergency services at the scene said Maraekakaho Rd would likely be closed "for a very long time".
- The Dominion Post