UPDATE 6AM MONDAY

New Zealand’s Department of Conservation has closed off a South Island beach covered in rotting whale carcasses, saying they could “explode” on volunteers.

The Southland Times reports that while Sunday had been a largely successful day of rescues, the dead whales remaining were a danger.

Conservation department staff and volunteers work to re-float the stranded whales. Photo: Dept. Conservation

DoC operations manager Mike Ogle said the carcasses were “just nasty”.

“These things explode from the stomach and if you’re standing right there it’s not very nice getting a ‘gut bomb’ on your face.”

On Sunday the department had better news, saying in a media update that 17 pilot whales that were part of a larger pod stranded on Saturday had been successfully turned around and sent into deeper water in Golden Bay.

“Two boats were used to guide the 17 whales out to rejoin the original diffuse pod and it is hoped that they will find a way into deeper, safer waters,” the statement said.

EARLIER

Volunteers are battling an environmental disaster in New Zealand, with hundreds of whales beaching themselves on the South Island.

The drama first unfolded overnight on Thursday when 416 whales stranded at Farewell Spit, with 75 per cent found dead on Friday morning.

At least 20 pilot whales were euthanised, while another 80 were refloated and joined a second pod of 200, according to the Department of Conservation.

But joy turned to despair with three new strandings on Saturday evening.

“The whole damn lot of them have come ashore,” a DOC spokesman said.

He said it was difficult to keep track of the whales’ movements, but that 50 had come ashore at one location and 70 at another.

“We are talking about a fairly major second stranding south of where we were,” the spokesman said.

In total, more than 650 pilot whales have beached themselves over a two-day period along a five-kilometre stretch of coastline at the tip of the South Island.

About 335 of the whales are dead, 220 remain stranded, and 100 are back at sea.

Department of Conservation Golden Bay Operations Manager Andrew Lamason said they were sure the second stranding involved a new pod because they had tagged all the re-floated whales from the first group and none of the new group had tags.

Volunteers were being called out again to try to keep the whales alive until an attempt to refloat them at high tide.

Hundreds of dead whales remained at the original stranding site, with Massey University pathologists carrying out necropsies to try to determine the cause of death.

Local iwi representatives Mairangi Reiher and Shane Graham have provided a karakia, or prayer, over the dead whales.

Volunteers pour water over the stranded pilot whales during a mass stranding at Farewell Spit. Photo: Getty

The decision to euthanise those whales that could not be refloated was made to relieve suffering.

“We are not able to successfully refloat stranded whales in every case. Even when some whales are saved, others inevitably die from injuries and the stress of being stranded, particularly the more they re-strand, as commonly occurs, and the longer it goes on,” DOC says.

Mass beachings are not uncommon at Farewell Spit, where it is believed the gently shifting sandy beaches may not be picked up by the whales’ echolocation.

Up to 300 whales are dead after being stranded overnight. pic.twitter.com/OfqkR1o2fg

— AJ+ (@ajplus) February 11, 2017

Officials will soon need to turn to the grim task of disposing of hundreds of carcasses. One option being considered was to tether the carcasses to stakes or a boat in the shallow tidal waters and let them decompose.

The problem with towing them out to sea or leaving them was that they could become gaseous and buoyant, and end up causing problems by floating into populated bays.

Farewell Spit, a sliver of sand that arches like a hook into the Tasman Sea, has been the site of previous mass strandings. Sometimes described as a whale trap, the spit’s long coastline and gently sloping beaches seem to make it difficult for whales to navigate away from once they get close.

New Zealand Geographic reported pilot whales were the most common whale to beach in mass strandings on the country’s shores.

Between 1976 and 2000, 165 pilot whale strandings were recorded in New Zealand – half of them herd strandings – with 6000 whales in total running aground, it said.

This week’s event is the third-largest recorded in New Zealand since data started being collected in the 1800s.

About 1000 whales beached themselves on the Chatham Islands in 1918 and 450 in Auckland in 1985.