A group of 25 people were taking an organized guided tour of the Breidamercuryekull glacier when the cave collapsed, reports gazeta.ru.
"Four people are stuck under the ice, two have already been rescued, they are seriously injured," police in Sudurland said on Sunday.
"The search for two people trapped in an ice cave continues," the statement said.
Icelandic media reported that two helicopters of the country's coast guard were sent to the scene, as well as ambulances and police were called.
The glacier where the accident occurred is located near the Jokulsaurloon Glacier Lagoon, one of Iceland's most popular tourist destinations.
