"We're still not really sure about the nationalities," said Tariq Hassan, a spokesman for the Interior Ministry. He added that an investigation will be conducted into the sinking, which occurred about 9:30pm.

Bahraini officials said there was no indication the boat was attacked. Without elaborating, they said only that the boat experienced a "technical" problem.

Information Minister Muhammad Abdul Ghaffar said he estimates that the passengers included 25 Britons, 10 South Africans, 20 Filipinos, 10 Egyptians and 10 Bahrainis.

The passengers worked for the same company and were on an evening dinner cruise scheduled to last a couple of hours, Mr Ghaffar said. He added that the company was based in Bahrain.

The US Navy sent boats, a Coast Guard cutter, 16 divers and two helicopters to assist in the rescue, Navy officials said. The island kingdom houses the headquarters of the US Navy's Fifth Fleet, which patrols the Persian Gulf.

CNN