Icelandic rescuers worked by hand on Monday to cut through the remnants of a collapsed ice cave as they searched for two tourists missing for more than 24 hours after a glacier in the south-eastern part of the island caved in, killing one person and severely injuring another.

The search, which was suspended overnight when conditions made it too dangerous to continue, resumed at about 7am local time, Icelandic broadcaster RUV reported.

Video showed rescuers working inside two large craters surrounded by sand-blackened ice.

“We have three teams that take turns, working for an hour at a time scooping and breaking down ice,” Sveinn Runar Kristjansson, the local police chief, told RUV. “Meanwhile, of course, we’re still in this investigative work, figuring out who might be down there under the ice. This work continues.”

Local police said a group of 25 tourists from several countries were exploring an ice cave at the Breidamerkurjokull glacier in south-eastern Iceland when the incident happened shortly before 3pm on Sunday.

Four people were struck by falling ice, with one dying at the scene and another flown to hospital by helicopter.

Ice caves are a popular destination for visitors to Iceland, with tour operators offering customers the chance to “explore the insides of glaciers” and see the blue colour and “stunning patterns” in the ice.

“This is a terrible event that you don’t want anyone to go through,″ Gardar Hrafn Sigurjonsson, the association’s vice-chairman, told local news site Visir. “We regret this terrible accident on the Breidamerkurjokull, both me personally and the association.”

Visir said the group that was at the cave during the collapse was on an organised tour accompanied by a guide. Most of the visitors were outside the cave when it came down, it reported.

Glaciers cover about 11% of the territory of Iceland, an island nation in the north Atlantic that sits on the southern edge of the Arctic Circle.

The largest is Vatnajokull, which covers 3,050 square miles (7,900 sq km).

Breidamerkurjokull is a tongue of Vatnajokull that ends at the Jokulsarlon Lagoon, where icebergs constantly break off from the glacier.

Moving rescue equipment and personnel up to the glacier is difficult due to the rugged terrain, and rescuers had to cut through the ice using chainsaws.

The glacier is about 185 miles (300km) from a volcano that erupted on the Reykjanes Peninsula in south-western Iceland on Friday.