It is a mystery that could grace the pages of a thriller novel.
A cargo ship carrying timber worth $1.8m (£1m) from Finland to Algeria is apparently briefly hijacked off the coast of Sweden before continuing its journey through the English Channel - and then disappears.
Nothing has been heard from the Maltese-flagged Arctic Sea since its last recorded sighting on 30 July, and officials appear to have no idea where it could be.
If this event had occurred in the seas off east Africa, the finger would immediately have been pointed at Somalia's notorious pirates.
But the Arctic Sea disappeared while rounding the west coast of France, in what are considered to be the pirate-free shipping lanes of Europe.
And as a maritime hunt gets under way to find the 3,988-tonne vessel, speculation is rife over what might have led to the Arctic Sea's disappearance.
Was the ship carrying something other than timber, "something much more expensive and dangerous", as one expert put it?
Or is its disappearance down to some commercial dispute or even a quarrel between rival Russian mafia gangs, as other observers have suggested?
Pre-trip repairs
However, all the experts appear to agree that the ship could not have sunk, as floating wood or oil would have been seen by now. They also say this was no typical hijacking.
The Arctic Sea, carrying 15 Russian crew, left Finland on 23 July bound for the Algerian port of Bejaia.
“ It seems some third party didn't want this transit to be fulfilled so they made this situation highly sophisticated and very complicated ”
Mikhail Voitenko Editor of Russia's Sovfracht maritime bulletin
A day later, in the Baltic Sea, the ship was boarded by masked men who claimed to be Swedish anti-drugs police. They tied up the crew and searched the vessel, reportedly leaving about 12 hours later.
These events were reported to the Swedish police in a round-about way.
A police spokeswoman told the BBC that the ship's crew first alerted their shipping company to what had happened. The firm then informed Russian embassy officials in Finland, who contacted their counterparts in Sweden who informed the Swedish authorities.
The police spokeswoman would not comment on any alleged drug link to the ship, saying only that no line of inquiry could be ruled out.
But, while the true facts about what happened remain for now unknown, speculation about a Russian dispute that got out of hand is plausible, says David Osler who writes on maritime safety for Lloyds List.
"It doesn't look like it's a Somali-style hijack for ransom because there hasn't been a ransom demand," he told the BBC's Today programme.
"It doesn't look like it's the sort of theft of a high-value ship or high-value cargo… so the longer it goes on, the more it looks like some sort of dispute between Russian interests."
Mikhail Voitenko, editor of Russia's Sovfracht maritime bulletin, goes one further to suggest "the vessel was loaded secretly with something we don't know anything about".
He ruled out drugs or "illegal criminal cargo", adding: "I think it is something much more expensive and dangerous.
"It seems some third party didn't want this transit to be fulfilled so they made this situation highly sophisticated and very complicated," he told the Russia Today news channel.
He pointed out that the unknown cargo could have been loaded in Russia's Baltic Sea enclave of Kaliningrad, between Poland and Lithuania, where the ship underwent repairs before picking up its cargo in Finland.
The ship is operated by Helsinki-based Solchart Management, which is believed to be linked to the Russian firm Solchart Arkhangelsk. It is registered in Malta, under the name of a Russian company.
Calls to the head of Solchart in Finland, Viktor Matveyev, went unanswered, but there is no suggestion that either the firm or the crew knew or were involved in any illegal activity.
'Pretty much anywhere'
For now, there remain a lot of questions and few real answers.
Malta's maritime authority is leading the hunt for the ship. It said on Wednesday the ship had not tried to enter Gibraltar waters and so could be heading out into the Atlantic Ocean.
Russia has drafted in all its vessels in the Atlantic to help with the search.
Arctic Sea is equipped with an automatic tracking system, but this appears to have been either switched off or stopped working since its last signal on 30 July.
And where might the ship be now?
"It could be pretty much anywhere," says David Osler. "It's not a very fast ship so it can't have quite got as far as the Far East. But it could be near West Africa or South America."
Story from BBC NEWS:
http://news.bbc.co.u...ope/8199766.stm