ERR's online news in Estonia has published the 12-page letter (in Estonian) in full, which was signed by Lennart Berglund, head of the association in Sweden.

The letter points out that the precise cause and course of the disaster has yet to be identified, and that whilst a Joint Accident Investigation Commission (JAIC) was established to investigate the wreck of the Estonia, which lies on the seabed in international waters in the Baltic, roughly equidistant between Estonia, Finland and Sweden, nothing was completed and the final report was less than convincing, the letter says.

The letter claims that a number of new facts have come to light in the 21 years between the sinking and the letter's authoring; these facts seriously question the scientific validity of the JAIC's conclusions, and the reliability of the entire investigation. The letter also cites both international maritime regulations and Estonian law, both of which require the reopening of an investigation if new considerations arise, it says.

''In light of the above, the Government of the Republic of Estonia, as the state whose flag the Estonia sailed under, is asked to begin the process of a new, official investigation, aimed at identifying the cause of the shipwreck and the exact course of events,'' the letter states.

Since diving at the wreck is forbidden, any investigations following that by the offical joint committee unavoidably link back to the latter's verdict, meaning the reasons for the sinking have not been studied, only the feasibility of the official, joint committee's theory, the letter says.

Independent investigations question official account

Added to this is the fact that the ship's hull has never been systematically studied, documented or filmed or, if it has, these findings have not been made public, the letter continues.

In support of claims that the JAIC conclusions are unsatisfactory, the letter cites an investigation by  SSPA, a Swedish maritime solutions firm, which, working on behalf of Swedish national innovations agency Vinnova, stated that the JAIC version of events was only possible.

However, the JAIC description of the progress of the disaster fits better with a holed-hull theory, than the lost visor theory.

The official report indicated that locks on the bow visor of the ferry, which was designed to raise and lower while in port in order to take on vehicles, had failed under the pressure of waves in the stormy, separating both it and bow doors from the hull and thus allowing water to flow in.

This ties in with reports by survivors of several loud, metallic banging sounds heard in the minutes before the ship started first to list to starboard, and then to sink.

Furthermore, Berglund pointed out that the SSPA consortium, which investigated the accident on the instructions of the Swedish National Innovation Agency, Vinnova, concluded that the JAIC version was only feasible if substantially modified on some important points and ignored circumstances that had not been investigated. However, the JAIC description of the progress of the accident fits better with the hole-hull version than the lost visor version.

Another study commissioned by Vinnova also concluded modifications to the JAIC version were necessary for the theory to be feasible, but also differed in findings from SSPA's.

''On the basis of the above, it is clear that, even as of today, there is no consensual scientific knowledge on several key issues of importance to the accident. In other words, the laws of physics affecting the stability and buoyancy of the Estonia have not yet been established," the letter states.

"Therefore, the JAIC version - or any other version - cannot be trusted,'' it continues.

The offical report states that once the visor and bow doors had been compromised, even slight flooding by seawater on vehicle decks hampers a ship's ability to right itself after rolling with a wave, an effect in evidence in the capsizing in shallow water of the MS Herald of Free Enterprise off Zeebrugge, Belgium, seven years before the Estonia.

The letter also enumerates several facts related to the sinking which it says have not been investigated, which together provide a sufficient basis for the Estonian government to start a new, formal investigation.

The letter was also forwarded to the Ministry of Justice in Estonia, which returned with a refusal for a signature from then-justice minister Urmas Reinsalu (Isamaa), it is reported.

The victims' association now wants a new investigation into the disaster, and awaits preliminary hearings at Tallinn administrative court, it says.

Ministry of Justice response

ETV current affairs show ''Pealtnägija'' asked the justice ministry why no substantive response has been so far issued following the 2016 letter; spokesperson for the ministry, Maria-Elisa Tuulik, said that since accident regulations have been amended several times since the disaster, there has been a lack of legal clarity as to the issue of competence, though this is expected to be answered by the administrative court in due course.

Tuulik said that the ministry fully understands the victims' concerns, and expects the situation to be resolved in the near future.

''Certainly the state has to learn from the story how to improve communication and cooperation between the institutions of different states,'' she said.

The MS Estonia sank on September 28, 1994, somewhat west of the Turku archipelago, resulting in 852 fatalities from the 989 on board the ship, including its captain, making it the second-deadliest peace-time maritime disaster involving a European vessel, after the Titanic. 138 people survived the sinking, though one later died in hospital.

Wind speeds of 15 to 20 meters per second, and significant wave heights of 4-6 meters, were recorded in the vicinity at the time; on-site commander of the rescue effort, the captain of the Silja Europa, a ferry operating in the area which was one of the first vessels to arrive on the scene, described weather conditions as "normally bad" for the time of year.

The wreck, which lies in relatively shallow waters, was later encased in concrete, at the behest of the Swedish government, and an international treaty between Estonia, Sweden, Finland, Latvia, Poland, Denmark, Russia and the UK prohibited its citizens from even approaching the wreck. The Swedish Navy has however reportedly discovered diving operations at the site at least twice; the wreck is monitored by radar by the Finnish Navy.

Some reports have claimed that the ship was carrying explosives and that the detonation of these caused the disaster, something which was subsequently covered-up by the relevant governments, the theories state.