It was reported back in Feb 2016 that a "preliminary inquiry" had whown that the cause was not cargo shifting, but the authority was not identified.
The initial list and abandonment took place, as I understand it, in international waters (though she later drifted into French waters, hence being taken charge of by the French authorities. With no loss of life or reported pollution, and no othr vessel involved, I suspect that the responsibility for any enquiry would rest with the flag state, Panama.