MILAN (Reuters) - The number of migrants who died in the hold of an overcrowded fishing boat rescued on Saturday has risen to 49, the coast guard said on Sunday.

The bodies of the victims, along with the 312 survivors plucked from the boat off the coast of Libya, were due to arrive at the Sicilian port of Catania on Monday morning aboard the Norwegian ship Siem Pilot.

On Saturday the Italian navy said at least 40 migrants had died, probably from suffocation after inhaling fumes from fuel..

What is expected to the final tally was determined after all the survivors and victims were transferred to the Siem Pilot during the night.

Hundreds of other migrants were rescued from other boats on Saturday and were being taken to ports in Sicily, navy and coast guard officials said.

More than 2,300 migrants and refugees have died so far this year in attempts to reach Europe by boat, compared with 3,279 deaths during the whole of last year, the International Organization for Migration (IOM) said on Friday.

IOM spokesman Joel Millman said nearly a quarter of a million migrants and asylum seekers had arrived in Europe via the Mediterranean so far this year, compared to 219,000 for all of 2014.

(Reporting by Stephen Jewkes; Editing by Angus MacSwan)