Attorneys for Justice for Concordia said Saturday the investigation involves allegations of collusion in the 2012 grounding of the ship, which killed 32 people.
Prosecutors confirmed the investigation but told Italy's ANSA news agency the probe was "an obligatory move."
ANSA said investigators were looking at five individuals who were on the board at the time of the shipwreck. The investigation is in addition to the investigation into the Costa Concordia's captain and crew members.
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