The Smyrni was carrying 135,000 metric tons of oil to Somalia when contact was lost Thursday night.
The waters off the Horn of Africa are frequently prowled by pirates despite the presence of a European Union naval task force assigned to protect the shipping lanes. The BBC said at last count there were about 17 ships and nearly 300 sailors being held for ransom by pirates in Somalia, the BBC said.
The Liberian-flagged Smyrni carried a crew of about 15 Filipinos and Indians. The vessel was launched just last year and was on only its second voyage when it was captured.