There are fears for the safety of visitors to New Zealand volcano Whakaari, or White Island, after an eruption on Monday afternoon.
The volcano, located around 40km offshore of the Bay of Plenty, sent huge amounts of white smoke - most likely steam - into the air from around 12:10pm AEDT.
Prime Minister Jacinda Ardern said the latest advice provided to her was that around "100 people were on or around the island" and "some of those are unaccounted for".
Local reports suggested around 20 people could have been on the island.
Helicopters have been dispatched to assess the situation.
Whakatane mayor Judy Turner confirmed the eruption produced injuries.
"There have been some people who were on the island at the time, who have had some injuries," she told Radio NZ.
"I'm not sure of the extent or nature of those injuries and that emergency services are all waiting for them to be returned from the island so they can attend to them."
Geological hazard trackers GeoNet had registered moderate volcanic unrest on the island for weeks.
The White Island Crater Rim camera, held by GeoNet, showed a string of people visiting the crater at that time.
Subsequent shots from the camera, displayed online every 10 minutes, show the blast rendered the camera inoperable.
Whakaari is New Zealand's most active cone volcano, and frequently visited by tourists.
The local council says New Zealand Police and Bay of Plenty Civil Defence are working together to respond.