Verified Answer :

 It was based on
computer modeling.  However the results
were inconclusive. Some believe that it could have been set off by coals from
within the ship. There is a suggestion based on the soil depression found in
the ship that a small mine could have been detonated.

The National Geographic findings on the sinking of the main were mostly based on advanced computer modeling. The advanced computer modeling refers to a technique that has represented a crucial shift on the creation of art and consists on constructing and manipulating abstract representations of an object simulated  with computer system.