A beach in New Zealand has become a graveyard for pilot whales.

According to reports, around 650 whales were stranded near Puponga, on the Golden Bay shore of Farewell Spit last week. The officers and volunteers tried to save as many whales as they could by refloating them back to the sea. Unfortunately, 400 of them did not make it.

While whale stranding in New Zealand is not a new occurrence, the latest strandings are the largest the country has witnessed so far since the 19805. In an interview with BBC, a resident said whale carcasses have been a seasonal sight.

"There's a lot of theories out there as to why it happens, but at the end of the day I think there's four or five hotspots where they strand [in New Zealand], and the one thing they all have in common is shallow water," Gary Riordan said. He added that whale stranding is seasonal and usually happens around January and February. 

Reuters reported that the New Zealand Department of Conservation (DOC) has issued a statement early this week, closing the beach and warning the public about carcasses that might explode on the beach.

To address the situation, the workers started to pop the carcasses one by one using knives and needles to slowly release the internal gas pressure and prevent the bodies from exploding.

Meanwhile, as of Tuesday, most carcasses had already been moved onto sand dunes. It would take several months before their bodies would rot and decompose. Other whales were left in the areas where they were because the excavation machine could not reach their location.

New York Times notes that the reason for the massive stranding is still unknown and Massey University in New Zealand are planning to study some of the dead animals to learn how they had died.