The aftermath of the collapse of a five-storey milk silo at Fonterra's Edendale plant sounded a 747 flying low overhead, a neighbour said.
A Fire Service spokesman said a five-storey high raw milk silo collapsed at the Southland plant due to an explosion about 1.50pm today.
The tower and gantry bridges at its top "completely collapsed'', he said.
Fonterra chief operating officer global operations Robert Spurway said all staff members were safe following the collapse.
"Our teams were able to quickly confirm that all of our people were accounted for, which is always our first priority in any unexpected event,'' Mr Spurway said.
The silo was one of about 100 silos on site, representing less than 10% of Edendale's total capacity for raw milk storage.
While the cause of the incident was not yet known, Mr Spurway confirmed there was no explosion.
He said the silo appeared to have failed and the subsequent collapse damaged a nearby pipebridge, creating the loud noise heard by those in the vicinity.
"Whilst some of the damage may take several weeks to repair, the situation is under control and we are now working to get the plant back up and running as normal,'' he said.
There could be some temporary impact on milk collection in the Southland region, and it would keep impacted farmers informed.
A person who works at a business about 200 metres away said power flicked on and off after the initial bang, which was followed by steam being released.
The initial bang was loud, but the steam being released was much louder and sounded like a 747 flying low overhead.
A Fire Service command unit from Invercargill as well as six appliances from Edendale, Wyndham, Mataura, Gore, Kingswell and Invercargill were on site.
A St John ambulance and first response unit were also on standby at the plant.
The NZ Transport Agency said State Highway 1 at Edendale was closed just after 2.30 pm
The detour route for light vehicles was Hilda and Homestead Roads.
There was no suitable local detour for heavy vehicles, which will be queued if they reach Edendale.
If possible drivers of heavy vehicles should detour via State Highways 6 (north of Invercargill) and 96, through Winton.
Southbound truck drivers should turn off at State Highway 96, south of Mataura, and avoid Edendale, says the Transport Agency.
