Head of the Estonian investigation team Rene Arikas said that: "The soil around the wreck is very unstable and further landslides cannot be ruled out," Arikas said, quoted by BNS.

Arikas was speaking at a press conference Tuesday following the 10-day preliminary survey of the wreck, which lies deck-down and on its starboard side, in around 100 meters of water, south of the Turku archipelago.

The initial survey's full results will not be available until the end of next year, however, by which time the main investigation, due to start in spring should it go ahead, will have been ongoing for several months.

Also speaking at the press conference, Sten Suuroja of the Geological Survey of Estonia (Eesti Geoloogiateenistus), added that: "The geological composition of the seabed is rather simple in the area of the wreck. It can be seen quite clearly that the middle part of the wreck rests on a hard bedrock."

Suuroja heads the department of marine geology and geophysics at the geological survey.

Investigator: Bedrock so hard it broke our drill

A 2020 documentary which aired on Swedish TV provided filmed footage evidence of a large, several-meter gash in the hull, one of several reported holes and a development which prompted speculation over the true cause of the 1994 disaster.

However, the hard bedrock may have been the cause of the ruptures as the stricken vessel impacted the seabed.

Rene Arikas added that: "The rock in the middle part of the wreck is so hard it broke our drill."

On the other hand, the softer material below the bow and stern of the wreck of the vessel – which measured over 155 meters when laid down – provide less support. One of the most focused-on findings of the initial dive was that the bow vehicle ramp, previously thought to have been in a "closed" position now lies fully open.

Sten Suuroja said that the survey was conducted with a boomer system, which beams acoustic waves to the bottom of the sea and measures the reflected signal, in order to provide information on sediment and rock on the seabed.

Bow ramp opened when vessel sank, closed on seabed impact

Arikas noted that the survey focused on damage to the starboard side of the vessel, the bow ramp and the car deck. The vessel's bulbous bow had sustained various damage and scrapes, he added.

"The origin of these areas of damage should be investigated further. With regard to the bow visor, we have conducted theoretical calculations and are planning to carry out a laser scan," Arikas went on, adding that the visor is currently located in a military compound in Sweden.

The official explanation of the sinking is that the ship's bow visor sheared off in heavy seas, allowing water to enter the vehicle deck and compromising the vessel's buoyancy.

The vehicle ramp itself first opened, striking the bow's protruding bulb, and then closed again when the vessel hit the seabed Arikas added.

"According to our knowledge, the ramp was only slightly open, and not fully. The 3D sonar showed, however, that we can see quite far into the wreck, into the car deck," he said.

Vessel's upper decks inaccessible

The preliminary survey aims to assess if there is sufficient basis for launching a further safety investigation, he added. This has yet to be determined.

A dive robot provided evidence that only a small part of the ramp is still attached to its hinge, while the ramp as a whole has, as noted, fallen fully open, for reasons still to be established.

The force that caused damage in the side of the hull, on the other hand, would have to be "enormous", Arikas said, adding that the exact extent of the damage is not known as it could also reach below the hull; the ferry's seventh and eighth decks (of 10) remained inaccessible, he said.

The dive robot also found significant volumes of debris inside the car deck, though it was not able to penetrate further inside, while some of the damage in the hull plating are on the opposite side from that which struck the seabed first, Arikas said.

Stern ramps remain closed

A deformation of 22 meters in length and four meters in height was registered in the middle part of the vessel on the starboard side.

The vessel's plating has outward deformations as well as in some inward ones, while a side fender has been forced inside the vessel. The deformations generally match the local geological profile.

As to the stern, its ramps had remained in a closed attitude.

The wreck rests on a slope with a gradient close to 30 meters. There is a protruding outcrop near the middle segment of the vessel, on which it rests on its starboard side – a fact already known in 1996 after the first investigation.

The soil around the wreck has collapsed on four occasions at different times.

The dive had seen interference which reduced sonar penetration from 150 meters, to 20 meters later on in the investigation.

Some objects lying close to the wreck also need to be identified, while a device left behind to measure sea current speeds will need to be retrieved in due course to extract data, Arikas said.

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