The Estonia, operated by the Estlines ferry company, was en route from Tallinn to Stockholm on September 28th 1994 when it sank, claiming 852 lives, including those of 501 Swedes.
The direct cause of the accident was the failure of locks on the bow visor, which allowed water onto the car deck, destablising the ship.
Witnesses have spoken of hearing an explosion, and many claim that this was the underlying cause of the ship’s sinking. A former customs officer claimed in 2004 that the Estonia had been used by Swedish military intelligence to import secret military equipment from Russia.
The two research teams, one Swedish and one German, were asked by the Swedish government to study how the ship could have sunk so quickly.
Professor Olle Rutgersson of Chalmers University of Technology in Gothenburg, leading the Swedish research team, told Swedish Radio it cannot be ruled out that a hole was blown out of the ship by an explosion.