Ude, who is involved both in a private sector expedition aimed at surveying the wreck of the MS Estonia and was also involved in the official investigation whose preliminary dives took place in July, says the devices could have been the source of disturbance experienced in a wreck survey in the summer work.

He said: "The very idea of these devices is to send out alternating signals that makes it possible to triangulate the Autonomous Underwater Vehicles' (AUV) position," referring to remote dive robots used heavily in modern-day investigations of this nature.

"They have been left in place to fix the position of the hull and avoid potential mistakes installing new ones," Ude, who took part in the official Estonian Safety Investigation Bureau's expedition this summer, said.

"Looking at the direction of the noise, there is a 90 percent chance the beacons were operational when we were trying to get our images," he continued, adding that devices of this kind can be remotely activated and deactivated.

One of the most mysterious aspects of the putative sea-floor devices is where their power source is drawn from.

"I cannot tell you what triggered them and caused them to interfere with our work the last time," he went on, though said that the beacons, which would likely be expensive, would overall make surveying easier.

Ude said an autonomous underwater vehicle (AUV) he was controlling had happened upon three peculiar metal constructions topped by what appear to be lighthouse-like columns, or in other words beacons, lying about 100 meters due north of the wreck.

They may have been put in place when now-abandoned plans to encase the wreck, which lies in around 100 meters of water south of the Turku archipelago, in concrete.

The beacons would be capable of emitting signals from fixed geometric positions to facilitate more precise navigation in otherwise difficult conditions.

The plan to entomb the wreck saw preparatory work such as coverings of sand and pebbles, but due in part to protests from victims' relatives, it was ditched. The very fact there were plans to so treat the wreck have also fueled conspiracy theories about the vessel's fate and the cause of her sinking.

Headed by former investigator and former state prosecutor Margus Kurm, the private sector dive is funded in party by the Postimees Group, which operates the daily newspaper of the same name, newswire BNS, TV channel Kanal 2 and other concerns. As such, critics have suggested the project is as much a way of generating news as of getting to the bottom of what happened with the ferry.

The official joint Swedish-Estonian dive saw its preliminary work take place in summer, followed by a break, and will resume next year. Conditions in autumn and winter are unsuitable for work of this kind, and recent examination by the Postimees Group-funded investigation involving human divers yielded very little, due to poor visibility and conditions.

The MS Estonia sank in the small hours of September 28, 1994, while en route from Tallinn to Stockholm. The sinking is the largest maritime disaster in peacetime in the Baltic Sea, killing 852 people from 17 countries, and second-largest peacetime maritime disaster ever, so far as European vessels go, after the Titanic. 137 people survived.

--

Follow ERR News on Facebook and Twitter and never miss an update!