Cruise ship security card records have led Italian authorities to suspect that missing Dublin-based mum, Xing Lei Li did not leave the ship.
Records from the key card used to get on and off the vessel could prove crucial in the investigation, after her husband claimed Ms Xing left the ship of her own accord.
Ms Xing (38) has not been seen since February 11 and is feared dead, with her husband, Daniel Belling in custody in Rome on suspicion of her murder.
Mr Belling (45) was arrested when attempting to board a Ryanair plane from Rome to Dublin - where the couple have lived - on February 20.
Speaking on behalf of his client, Mr Belling's lawyer, Luigi Conti has said Ms Xing left the ship, with her husband believing she either went to China or Dublin.
The couple have an address at Clare Hall in north Dublin.
Mr Belling has claimed that he last saw his wife when the MSC Magnifica docked on the Katakolon island in Greece - and that after embarking on a day trip with his kids, she was not there on their return.
However, Italian police now suspect Ms Xing never exited the ship, as her key card did not register on the security card system. The system is used to allow residents on the cruise ship to leave and board the boat.
It is understood that CCTV footage from the ship is being examined, while Italian authorities have also conducted a number of interviews with staff who were working on the ship for the duration of the cruise.
One member of staff working at the restaurant on the cruise ship is said to have told investigators that he last saw Ms Xing dining with her family on February 10 when the ship was between Genoa and Valetta.
The staff member saw Mr Belling sit at the same spot in the restaurant with his two children for the duration of the cruise - between 6pm and 8pm each night - but says Ms Xing was not present.
Police authorities in Rome are also investigating a missing bag belonging to Ms Xing.
All luggage belonging to family has been recovered, apart from one of Ms Xing's.
The orange and grey suitcase was spotted with Ms Xing when she joined her family on a day trip in Genoa on the trip.
The photographs were taken from Mr Belling's phone.
Ms Xing's mobile phone is also yet to be recovered.
Since his arrest, Mr Belling has been locked up at the Regina Coeli - Rome's largest prison - with authorities unwilling to allow him to be released, as he is deemed to be a flight risk. Meanwhile, the couple's two Irish children remain in the care of Italian social services.