The bodies of two people missing and presumed dead since a New Zealand volcano erupted last week  may never be found, authorities said Wednesday.

Deputy Police Commissioner Mike Clement said he was “deeply sorry” that the bodies of local tour guide Hayden Marshall-Inman, 40, and Australian tourist Winona Langford, 17, have not been recovered.

He said the bodies were probably swept out to sea. “The reality is we have to wait for Mother Nature to produce those bodies. It may and it may not,” Clement said.

The White Island Volcano, also known as “Whakaari” in the Maori language, erupted on Dec. 9 while dozens of tourists were visiting the island, located about 48 kilometers off the coast of New Zealand’s North Island.

At least 16 other people were killed and more than 20 survivors suffered severe burns.

New Zealand Prime Minister Jacinda Ardern said this week that official inquiries by coroners and work safety regulators into the eruption could take up to a year, and will carry potential criminal penalties of up to five years in jail.

There has been much criticism of why tourists were allowed on to the country’s most active volcano.