There has been much speculation over what actually happened on the ship
Russia's top investigator has said a ship that went missing for more than two weeks will be searched to check that its cargo was legitimate.
In comments to the Rossiyskaya Gazeta newspaper, Alexander Bastrykin said he did not exclude the possibility that it was carrying more than timber.
The vessel, the Arctic Sea, was found on 16 August off West Africa, having apparently being hijacked.
There has been much speculation it may have been carrying weapons for export.
Eight people, mainly from Estonia, are still in custody in Russia on suspicion of hijacking the vessel.
The 4,000-tonne Maltese-flagged Arctic Sea set sail from Finland in July with a crew of 15, and was said to have been carrying timber worth $1.8m (£1.1m).
"We do not rule out the possibility that [the Arctic Sea] might have been carrying not only timber," Mr Bastrykin, the head of the investigative committee, was quoted as saying on Tuesday.
"This is why we need to examine the vessel - so that there are no dark spots in this story."
The ship had been scheduled to dock in the Algerian port of Bejaia on 4 August, but never arrived.
It was eventually found by the Russian authorities 300 miles (480km) off Cape Verde in the Atlantic Ocean.
The Russian crew have said they were boarded by up to 10 armed men as the ship sailed through the Baltic Sea on 24 July, but the intruders were reported to have left the vessel on an inflatable boat after 12 hours.
Speculation in the Russian media about what happened to the ship has included suggestions of piracy, a mafia dispute, a commercial row, smuggling or trafficking.
Those detained on suspicion of hijack have said they are environmentalists who boarded the ship for safety during a storm.