There are several issues that arise in the wake of a deadly volcanic eruption at White Island in New Zealand on Monday.

It says the new zealand prime minister, Jacinda Ardern, on Tuesday.

Among other things, the question of why tourists were allowed to walk on the active volcano, which in recent weeks has shown a heightened alert level.

Five people are already confirmed dead, while eight others - including new zealanders and tourists from Australia, Uk, USA, China and Malaysia - are still missing.

- There will be asked questions which must be answered by the relevant authorities, says Jacinda Ardern on Tuesday morning local time for Radio New Zealand.

According to the prime minister, the volcano has been active for several decades.

Professor Ray Cas from the department of earth, atmosphere and environment at Monash University in the australian city of Melbourne call the White Island "is a disaster that has been waiting to happen for many years".

- After that I visited the place two times, I have always felt that it was too dangerous to allow the daily tourist groups visiting the uninhabited volcanic island by boat and helicopter, he says.

In november raised the the authorities the alert level for the outbreak on the volcanic island of White Island to the two, because researchers had observed the increasing volumes of sulphur dioxide - a principal indicator of rising magma deep inside the volcano.

on Monday afternoon local time the alert level was raised to four, which is the second-highest step on the scale

Until november, the alert level remained at level one since the last eruption in 2016.

- It is an unpredictable, live volcano, says Jacinda Ardern on Tuesday.

White Island is privately owned, and it is up to the tour managers to decide when they take tourists out to New Zealand's most active volcano.

volcanic island located in the Pacific Ring of Fire. Ildringen is the term for the belt of volcanoes that are located along the asian and american stillehavskyster.

About four-fifths of all the world's earthquakes and volcanic eruptions take place in the belt.

One of the turarrangørerne to the island - White Island Tours - writes on its website that it organises trips to the volcanic island during the different alarm levels.

However, "passengers be aware that there is always a risk of the outbreak, regardless of the alert level".