Russian authorities questioned crew members from the Arctic Sea cargo ship after the seamen and eight alleged pirates were returned to Moscow on Thursday, adding new details to the mystery of the ship's monthlong odyssey.

Three heavy-lift air force jets, reportedly carrying 11 crew members, the alleged hijackers and other investigators, arrived at a Moscow region military base after flying from Cape Verde, the West African island nation where a Russian frigate stopped the ship four days ago.

The saga of the Maltese-flagged freighter, which left Finland on July 21 carrying a load of timber to Algeria, has gripped much of Europe. The ship was found nearly two weeks after it was to have docked in Algeria, thousands of miles off course and long out of radio contact.

Speculation on what was behind the freighter's diversion was heightened by the involvement of the Russian navy, the slow trickle of information and claims that news media were fed bogus information about the ship.

It was unclear why three planes were needed to fly such a small group of people to Moscow, nor why Il-76s — among Russia's largest planes — were used for the operation.

Federal investigators said in a statement that crew members told them that, while the Arctic Sea was in Swedish waters, the ship was boarded by eight men who wore uniforms that read "POLICE" on the back and who threatened the crew.

The statement did not give more details about the seizure or say if the men left the ship 12 hours later as earlier had been reported.

The Interfax news agency said the 11 crew members and hijackers were taken to Moscow's Lefortovo prison, run by the main KGB successor agency. It cited an unidentified law enforcement official as saying the crew members will be freed if the investigators confirm they were not involved in the hijacking.

State-run Vesti-24 television showed footage of what it said were air force planes arriving at the Chkalovsky base near Moscow, and men believed to be the hijackers being escorted roughly by special forces troops.

Earlier, men identified as Arctic Sea crew members told Vesti that the ship was seized in the Baltic Sea by gunmen. One unidentified man told Vesti that a crew member sent a text message saying the ship had been hijacked, but the hijackers then forced the captain at gunpoint to report that everything was normal on board.

Vesti also showed men in handcuffs, whom it identified as the suspected hijackers, being led by Russian marines to buses in Cape Verde. Russia has said four were citizens of Estonia, and the others were from Russia and Latvia.

There were conflicting statements about the fate of the Arctic Sea and its euro1.3 million cargo of timber. The Foreign Ministry said that the ship's captain and three remaining crew members stayed behind to help in return the ship to its owner.

The Kremlin said the ship was en route to the Russian Black Sea port of Novorossiisk, but federal investigators said it was drifting off Cape Verde.

More than a week after the Arctic Sea's departure from Finland on July 21, Swedish police said they had received a report that masked men had raided the ship in the Baltic Sea and beaten the crew before speeding off 12 hours later in an inflatable craft.

The freighter gave no indication of any difficulties or change in its route during radio contact while passing through the English Channel on July 28. Signals from the ship's tracking device were picked up off the French coast late the next day.

Swedish authorities last had contact with the ship July 31 in a brief telephone call with a person who identified himself as the captain, according to police spokeswoman Linda Widmark.

"It was a very short phone call, it was cut off, but it seemed as if everything was normal," she told The Associated Press.

The ship had been due to dock in Algeria on Aug. 4. Eight days later, Russian President Dmitry Medvedev ordered the Defense Ministry to take "all necessary measures" to search for the ship — raising suspicions that the ship may have carried more than just timber.

Arctic Sea was operated by the Finnish company Solchart, which has Russian management and a sister company providing technical support in the Russian city of Arkhangelsk, the home of all 15 crew members.

Officials have said the hijackers demanded a ransom and threatened to blow up the freighter if their demands were not met. A Russian company, Renaissance Insurance, said it received a ransom demand for $1.5 million Aug. 3.

But Russian and European maritime experts have cast doubt on the ransom reports and speculation has grown that the freighter was carrying contraband cargo, possibly weapons or drugs — suspicions fueled by dearth of information from the Russian government.

Yevgeny Limarev, a former Russian security agent who is now a French-based consultant on Russian security affairs, said the Arctic Sea was likely at the center of a struggle between competing business and Kremlin clans in Moscow, and the Kremlin was forced to intervene to prevent an international scandal.