Scores of passengers are still missing after a ferry sank early Thursday off the northern coast of Papua New Guinea.

Nerae Marimahu, a spokeswoman with the Pacific nation's National Maritime Safety Authority in Port Moresby, told VOA the MV Rabaul Queen sank about 16 kilometers off Cape Fortification. She said it was not immediately clear why the ferry sank.

The maritime agency says at least 300 passengers were believed to be aboard the ferry when it sank.

Australia's maritime authority has dispatched a special plane to help in the rescue efforts. A spokeswoman for the authority says more than 230 people have been pulled alive from the waters.

Several merchant ships have also been deployed to assist in the search for survivors.

The ferry's operator says it lost contact with the vessel as it was traveling between the island of New Britain and the town of Lae.

Australian Prime Minister Julia Gillard described the disaster as “a major tragedy” and said her country was helping Papua New Guinea respond.