Croatia's police official Josip Celic said on Wednesday that a police investigation was under way into the causes of poisoning that led to the death of an adult Italian citizen on a yacht off Hvar on Tuesday morning, while another five tourists on the yacht were helicoptered to the hospital in Split for treatment.

The two children – aged five and 14 — who were among the hospitalised patients were with a life-threatening condition, and the hospital authorities reported on Wednesday morning that they were still in a critical condition.

Details about the tragedy are still emerging.

Food or carbon monoxide poisoning?

First media reports speculated on Tuesday that the causing of poisoning might have been connected to food which they had eaten in a restaurant on Hvar, and those reports alleged that it could have been connected to eating a plate of mussels. However, the information that later appeared said that the air conditioning system on the yacht may have been the cause as the patients, admitted to the Split hospital, had inhaled carbon monoxide probably while staying in the yacht’s cabins.

On Wednesday morning, Doctor Branka Polic of the Split University Hospital Centre said that the two Italian children were still in an extremely critical condition and that the findings of laboratory blood tests of those patients showed that they had been probably poisoned by carbon monoxide.

The children needed mechanical ventilation due to multiple organ failure.