The probe of the Comoros-flagged Baltic Sky and its seven-member crew will seek possible terrorist or criminal links, said Greece's merchant marine minister, Giorgos Anomeritis.
"Someone could think that it would have some connection with terrorist groups," he told reporters in the port of Piraeus, near Athens. "That is why we stopped it when it entered Greek territorial waters."
Greek authorities have been tracking the vessel since it picked up the explosives and 8,000 detonators and fuses in Gabes, Tunisia, on May 12, he said. It was boarded by coast guard special forces Sunday after it entered Greek territorial waters in the southern Ionian Sea.
Anomeritis said the ship was carrying TNT, but shipping documents provided by Greek officials described the cargo as a commercially manufactured ammonium nitrate-based explosive, known as ANFO, often used in mining and construction. The reason for the discrepancy was not immediately clear.
The ship's manifest said the cargo was bound for a company in Sudan, but Greek officials claim it was only a post office box address. No other details of the firm were given.
"No one knows the recipient, so no one knows how it would be used," said Anomeritis, who left open the possibility that the ship was caught in a business deal that collapsed.
The crew of five Ukrainians and two Azerbaijanis were detained and could face charges of illegal transport of explosives and entering Greek waters without declaring a hazardous cargo, officials said.
"It should have declared that it was sailing with a cargo that was like an atomic bomb," said Anomeritis.
The vessel was seen near Istanbul, Turkey, on May 22 and crossed into the Aegean Sea on June 2, Anomeritis said. The Greek coast guard, acting on a tip from security officials in Greece and abroad, forced the Baltic Sky to dock Sunday in the tiny port of Platiyali, 145 miles northwest of Athens.
The port was picked because it is far from large population centers, Anomeritis said.
"We want this cleared up as soon as possible and the ship removed because of its cargo," said Pythagorus Samaras, the mayor of Astakos, a small town near Platiyali.
Concerns about terrorism have escalated following recent bombings in Saudi Arabia and Morocco. In Kenya, the U.S. Embassy was temporarily closed Friday and air traffic was restricted after the terrorism threat level was raised.
According to the Merchant Marine Ministry, the 37-year-old ship is registered to Alpha Shipping Inc. based in the Pacific Ocean nation of Marshall Islands. The Comoros, a nation off the southeast coast of Africa, is used by shipping companies as a so-called flag of convenience to avoid taxes and other regulations.
By Miron Varouhakis