LONDON (AP) — Icelandic authorities searched Monday for two tourists missing since an ice cave partially collapsed the previous afternoon, killing one person and injuring another.

The search, which was suspended overnight when conditions made it too dangerous to continue, resumed at about 7 a.m., Icelandic broadcaster RUV reported. Up to 60 researchers are already on the scene, with more expected to arrive throughout the day, RUV said.

Local police said a group of 25 tourists from several countries were exploring an ice cave at the Breidamerkurjokull glacier in southeastern Iceland when the incident occurred shortly before 3 p.m. Sunday. Four people were struck by falling ice, with one dying at the scene and another flown to the 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 color and “stunning patterns” in the ice.

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 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.

Local news site Visir said the group that was at the cave during the collapse was on an organized tour accompanied by a guide. Most people were outside the cave when it collapsed, Visir reported.

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 chain saws.

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