Story highlights Italian navy said 40 migrants dead, more than 300 rescued

More than 2300 migrants have died in 2015 attempting to cross the Mediterranean Sea

(CNN) At least 40 migrants died attempting to cross the Mediterranean and another 312 had to be rescued, the Italian navy said after encountering their boat Saturday.

Additional details about how the 40 died were not immediately available.

The navy said that it had transferred the survivors to the Norwegian supply ship Siem Pilot, which is patrolling the central Mediterranean as part of the ongoing European Union effort to assist seafaring migrants.

Last month the Siem Pilot ferried 785 migrants safely to port after the Italian coast guard rescued them from a wooden boat and a rubber dinghy off the Libyan coast.

Saturday's episode is the latest in a string of disasters in the Mediterranean in what has been a deadly year for migrants at sea.

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