The Department of Conservation says it is very unlikely seismic surveying had anything to do with the deaths of 12 sperm whales on a South Taranaki beach last week.
A camp manager noticed the whales on Thursday morning and the Department of Conservation and local hapu Ngati Tu were called.
DoC said a number of people had asked if the deaths were related to seismic surveying in the area, which finished in March.
"Given the time that has lapsed DoC considers it extremely unlikely that seismic surveying contributed to the death of these animals," said DoC marine species manager Ian Angus.
A veterinary pathologist from Massey University estimated the whales had been dead for 36 hours when he arrived at Kaupokonui Beach on Friday.
Angus said that meant necropsies to determine how they died were not possible.
"Standard samples were taken for scientific analysis but these are unlikely to reveal the cause of death.
"So, at this stage we don't know why the whales died and it is probable that we never will know for sure."
Some of the whales have been prepared for burial. Others, because of the rugged coastline, would be left for nature to take its course.
DoC said there had been 13 mass strandings of sperm whales since 1895. The largest was in 1974 in Muriwai when 74 sperm whales stranded.
No one knows why the whales strand.