Thousands of dead pipi have washed up on Waihi Beach in the Bay of Plenty, shocking the locals.
A video shot by resident Jeannette McCallum on Tuesday shows the sea of dead pipi lying on the beach.
Ms McCallum says she found the blanket of shellfish during a walk with her friend, and in some places the pipi were 20 centimetres deep.
"We couldn't avoid walking on them and when you did, it was just horrible; your feet sunk into them," she says.
"They were really thick around the stream that comes from the reservoir and onto the beach."
It is unknown what caused the die-off, but the Ministry of Fisheries says a lot of silt or sediment washed down by floods can make feeding difficult, or even smother shellfish beds.
The video, posted online, has been inundated with comments of concern and confusion.
"I noticed a whole pipi bed washed up two weeks ago in the same spot - such a sad sight to see the waste of our precious kaimoana! Would love to know what caused this," one person commented on the clip.
The footage has been viewed more than 51,000 times on Facebook and has been shared more than 830 times.