An investigation is underway in Tonga to find out how 600 litres of diesel have gone missing from the MV 'Otuanga'ofa at Queen Salote Wharf in Nuku'alofa.
The general manager of the boat's owner, the Friendly Island Shipping Agency, is not making any comment on the matter except to say that the company is investigating.
But the Tonga Broadcasting Corporation reports that while the ferry was docked over Easter there was a drop in the amount of fuel on board.
The boat's chief engineer is reported as saying he's keeping an open mind because the tilt of the vessel can cause a discrepancy in numbers.
The MV'Otuanga'ofa was bought to replace the ferry Princess Ashika which sank in 2009, killing 74 people.