Investigators are said to be focusing on the possibility that the absence of a valve or 'sea-cock' could have been responsible sinking of Asgard II.
It is not thought that the ship collided with a rock or other object, as none of the crew or trainees on board reported feeling any bump.
The French and Irish authorities are trying to find out why the 27-year-old training ship sank after it was rapidly overcome with water in the Bay of Biscay off the French coast.
Insurers are also carrying out their own investigation. All of the 25 crew and trainees were evacuated and rescued by French lifeboats.
Divers have not yet made it to the seabed where the Asgard II lies, about 100 metres deep, and its not known if it broke on its way to the bottom.
The sea is very choppy in the area, and it is uncertain if the wreck can be taken to the surface.
The cost of bringing the vessel above the water line may also be prohibitive.
