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

The search, which was suspended overnight when conditions made it too dangerous resumed at about 7 a.m., Icelandic broadcaster RUV reported. Video showed rescuers working inside two large craters surrounded by the sand-blackened ice of the Breidamerkurjokull glacier.

“We have three teams that take turns, working for an hour at a time scooping and breaking down ice,” Sveinn Rúnar Kristjánsson, 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.”

Police said a group of 25 tourists from several countries were exploring an ice cave at Breidamerkurjokull when it collapsed shortly before 3 p.m. Sunday. Four people were struck by falling ice, with one dying at the scene and another flown to a hospital in Reykjavik, the capital, by helicopter. Authorities haven’t released the names or nationalities of the victims.

The Association of Icelandic Mountain Guides on Sunday called for a full investigation and tighter regulations on ice cave tours. Glacier trips during the warmer summer months can be very dangerous, the association said.

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 color and “stunning patterns” in the ice.

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

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

Glaciers cover about 11% 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 7,900 square kilometers (3,050 square miles). 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 was difficult due to the rugged terrain, and rescuers had to cut through the ice using chainsaws.

The glacier is about 300 kilometers (185 miles) from a volcano that erupted Friday on the Reykjanes Peninsula in southwestern Iceland.

(AP)