The Quotidiano daily said fire crews had boarded the vessel from two pilot doors on deck three on 10 January after temperatures dropped.
The first three decks were then ventilated.
A new fire had started last week on the 26,900-gt Visemar-operated ro-pax (built 2009).
Salvors had been unable to remove the 1,200 tons of fuel still on board.
At least 11 passengers are known to have died when the vessel caught fire on 28 December, although the exact number remains uncertain.
