A cargo ship on which went through the English Channel disappeared shortly afterwards and international efforts are underway to find it, including the use of a Russian warship. Swedish authorities had already reported suspect activity on the ship.
CNN reports that the search is the first of it kind in Europe as there have been no reported hijackings of cargo ships in European waters in modern times.
The ship, the Arctic Sea, was carrying a cargo of timber from Finland to Algeria, which meant it had to go through the English Channel, an extremely busy shipping lane.
It signalled its presence in the Channel according to maritime regulations, but was not tracked after it left the Channel's authority and it subsequently disappeared.
The Arctic Sea is flagged in Malta, crewed by Russians, Latvian-owned and operated by a Finnish company.
Russian President Dmitry Medvedev ordered the Russian Defence Ministry to find the missing vessel and free it if necessary.
Russian naval forces are looking for the ship, and satellite tracking is also being used to help in the hunt.
The Swedish authorities have announced that the ship first aroused suspicion on July 24 when it was alleged to have been taken over off the Swedish coast by a group of 8 to 12 men posing as drug enforcement officers.
The crew was tied up and blindfolded before being interrogated about drug-running activities, they said. The interrogators went on to search the ship. Some of the crew are said to have been seriously injured at that time.
The crew said at the time that they believed the boarding was by genuine drug officials so no complaint was filed, said Swedish police sources.
The ship finally vanished on July 31 and did not arrive at its destination on Aug 4 as scheduled.
Several countries are involved in the hunt, and at least one Russian warship has been diverted to the search zone.
UK maritime experts say that although piracy has increased in other parts of the world, and notably off the East African coast, this would be the first hijack in European seas.
"Attacks on ships are extremely rare, basically they don't happen," said Jeremy Harrison of the British Chamber of Shipping.