Two world-renowned Finnish divers have arrived in the Maldives to help in search for bodies in an underwater cave tragedy that has already claimed five lives.

Medical research and insurance body DAN Europe said on Sunday it had appointed a “task force of specialists” to support the Maldivian National Defence Force search and recovery mission for the bodies of four Italian scuba divers still missing in a deep-lying cave in Vaavu Atoll.

Five Italians are believed to have died while exploring the cave, which is 50 metres underwater, last Thursday, according to Italy’s foreign ministry.

The recreational diving limit in the Maldives is 30 metres.

Only one body has so far been recovered. On Saturday, a Maldivian military diver died while searching for the four remaining bodies.

It is reportedly the deadliest diving accident the island nation in the northern Indian Ocean has recorded.

Maldives presidential spokesman Mohammed Hussain Shareef said that Mohamed Mahudhee, a member of the MNDF, died of underwater decompression sickness after being transferred to a hospital in the capital.

“The death goes to show the difficulty of the mission,” he said.

Earlier, Shareef said the searchers had prepared a plan based on their progress exploring the cave on Friday.

Mahudhee was part of the group that briefed Maldives President Mohamed Muizzu on the rescue plan when he visited the search site on Friday.

Rough weather has repeatedly hampered recovery efforts.

Italian Foreign Minister Antonio Tajani said everything possible would be done to bring the victims home.

His ministry said it was co-ordinating with specialist organisation Divers Alert Network to support recovery operations and the repatriation of the bodies.

The cause of the deaths remains under investigation.

Monica Montefalcone is among those believed to have died. Photo: AAP

The victims have been identified as Monica Montefalcone, an associate professor of ecology at the University of Genoa; her daughter, Giorgia Sommacal; marine biologist Federico Gualtieri; researcher Muriel Oddenino; and diving instructor Gianluca Benedetti, according to the Maldivian government.

Benedetti’s body was recovered on Thursday.

Montefalcone and Oddenino were in the Maldives on an official scientific mission to monitor marine environments and study the effects of climate change on tropical biodiversity, the University of Genoa said in a statement on Friday.

The scuba diving activity during which the deadly accident occurred was not part of the planned research and was “undertaken privately”, it said.

The university also said the two other victims – student Sommacal and recent graduate Gualtieri – were not involved in the scientific mission.

The bodies are in a cave that is 50 metres underwater. Photo: MDNF

Cave diving is a highly technical and dangerous activity that requires specialised training, equipment and strict safety protocols.

Risks increase sharply in environments where divers cannot head straight up and at depth, particularly when conditions are poor.

Experts say it is easy to become disoriented or lost inside caves, particularly as sediment clouds can sharply reduce visibility.

Diving at 50 metres also exceeds the maximum depth recommended for recreational divers by most major established scuba certifying agencies. Depths beyond 40 metres are considered technical diving, requiring specialised training and equipment.

Shareef said Benedetti’s body was found near the mouth of the cave. Authorities believed the remaining four had entered the cave.

Two Italians, a deep-sea rescue expert and a cave diving expert, are expected to join the recovery effort, Shareef said.

Finnish recovery divers Sami Paakkarinen and Patrik Grönqvist are also expected to be involved. They became internationally known through the 2016 documentary Diving Into The Unknown, which chronicled a 2014 cave-diving incident in Norway and the recovery mission undertaken by the surviving divers.

“The accident site presents highly complex operational characteristics,” DAN Europe chief executive Laura Marroni said.

“Access to the cave is located at a depth of between 55 and 60 metres, while the underwater system extends for hundreds of metres through multiple chambers and internal passages.

“The victims may be located in areas that are difficult to access, requiring extremely careful planning of every phase of the intervention.”

Italian officials said about 20 other Italians on the same expedition aboard the vessel Duke of York were safe.

Italy’s embassy in Colombo was providing assistance to those onboard. It has also contacted the Red Crescent, which offered to deploy volunteers to help provide psychological aid.

The Maldives tourism ministry said it had suspended Duke of York’s operating licence pending an investigation.

-with AAP