There is conflicting information on the possible whereabouts of a Russian-owned vessel with 15 crew members that has been missing since last month.
Earlier Friday, reports quoted military and maritime officials in Europe and Africa as saying the ship was sighted near Cape Verde, off the western coast of Africa.
But the Russian ambassador to Cape Verde was later quoted as saying those reports were not true.
Malta's Maritime Authority says it received a message July 24 that armed men disguised as police had taken over the vessel in the Baltic Sea. They apparently left without taking anything.
Concerns arose when the freighter and its reported cargo of Finnish lumber failed to arrive as scheduled in the Algerian port of Bejaia August 4.
The Russian navy has been scouring the Atlantic for the Maltese-flagged freighter, called the Arctic Sea.
Russian and Western maritime experts have put forth several theories, among them that the ship may have been carrying a secret cargo, was sunk for insurance money, or may have been seized by pirates.
It has been many years since there has been an act of piracy in European waters.
Some information for this report was provided by AFP and AP.
