Whales buried beneath New Zealand beaches could be releasing harmful toxins into the sand, a new study has concluded.

A 2009 thesis by AUT masters student Ann Bui studied the chemical effects of whale burial at Pakiri beach and Muriwai beach over six months in 2008.

Site samples will be processed by AUT professor of food microbiology John Brooks over the next few weeks.

But oceanographer Steve O'Shea, who was overseeing the project, said initial results show "massive spikes" in E coli bacteria 18 months after burial. He also suspected graves could house listeria bacteria.

"We've got 8000 whales buried under our beaches," he said. "Is there a ticking timebomb beneath the sand?"

O'Shea said whales are often buried just a metre beneath the sand.

He said problems could arise from beachgoers digging up rotting blubber or playing on areas with high levels of bacteria caused by shallow graves.