Twelve Britons and three people with dual nationality were among 57 people who died when a boat capsized overnight in the Gulf off the Bahrain coast, a Foreign Office spokesman confirmed today.
About 70 people were rescued after the two-deck Arabic dhow carrying 137 passengers overturned, possibly from overcrowding.
The Foreign Office spokesman said: "There are still other people unaccounted for, who may include British people." Officials have said the death toll could rise.
The boat, the al-Dana, was carrying a mix of Bahrainis, other Gulf Arab nationals and westerners, who were celebrating the completion of a construction project.
Witnesses said the boat had been overcrowded with passengers and that it had "rocked badly and tilted over" after hitting a wave.
Khalil Mirza, a Bahraini survivor, said: "People were scared in the water. They were fighting with each other and screaming."
At daylight, only the upturned hull of the dhow was visible in the water, with empty orange lifejackets bobbing alongside. Bahrain TV showed pictures of rescue workers using pickaxes to try to break through the hull of the vessel. No one had been found in the upturned boat.
Scores of officials and relatives waited at the harbour watching the rescue operation, which saw bodies being brought to shore covered with white sheets. Hospital workers took the bodies to waiting ambulances.
Survivors, still wet and in shock, squatted on the floor of a hospital. Several wept uncontrollably as friends and relatives tried to calm them.
Steve Harrison, the acting UK ambassador in Bahrain, told BBC news a number of "walking wounded" British and other nationalities had been brought ashore. He described the mood in the embassy as "sombre".
A Foreign Office rapid deployment team is on its way to the island state to support embassy staff and to offer help to survivors and their relatives.
The foreign secretary, Jack Straw, said he was "shocked" by the tragedy.
Abdullan al-Qubaisi, of the al-Dana company that owns the boat, told state television: "It has a capacity of 200, but it is allowed to carry only 100 passengers. They loaded the boat with more than its capacity. The captain refused to sail but they forced him to leave."
The coast guard commander, Youssef al-Katem, said 13 people were still missing. It was possible some people had tried to swim ashore, as the boat capsized less than a mile from the coast.
In addition to the Britons, the Bahrain interior ministry spokesman, Colonel Tarik al-Hassan, said earlier today, the dead included 17 Indian citizens, five from Pakistan, four from South Africa, three from the Philippines, two from Singapore and one from Germany. An Irish man is also among those killed in the accident, the department of foreign affairs in Dublin confirmed. The remaining dead had not been identified.
Murray and Roberts, the South African construction company that organised the boat party to celebrate the completion of part of the Bahrain World Trade Centre building, said 15 of its staff were safe but 10 had died in the sinking. They were four South Africans, three Britons, two Indian nationals and one Pakistani.
The chief executive, Brian Bruce, said the company had 25 employees in Bahrain, including 11 Britons. "We are deeply shocked by this tragedy. Our sympathy and condolences go out to all those who have been affected," he said.
Two other expat firms, WS Atkins and Nass, involved in the building of the World Trade Centre had staff involved in the disaster.
Atkins said five members of its Bahrain-based staff and three partners or relations had been confirmed dead. One staff member and a relative are still missing.
A worker at Delmon Readymix confirmed that its staff were also involved but did not give any additional details.
The Bahraini coastguard chief, Youssef al-Katem, said the guests had attended a dinner party aboard the ferry. They dined while the boat was still docked, and it then set sail. Up to 20 people disembarked before it left the dock, he said.
The boat capsized at about 9.45pm (1845pm GMT), less than a mile from shore.
Mr al-Katem said a survivor first alerted authorities to the accident via his mobile phone.
Raymond Austin, an employee of Delmon Readymix from Kent, told the BBC he had disembarked before the boat set sail. His daughter said he and two colleagues had decided to take the employees off the boat because the number of people aboard had made them fear for their safety. Mr Austin was "shaken up and distraught" after hearing the boat had sunk.
A Bahraini health ministry official, Nabeel al-Ansari, told Reuters most of those admitted to hospital had already been discharged. "Initially there were 33 brought by rescue teams; 31 were discharged and two have been admitted, both Indian," he said. "One Indian has a serious brain injury."
Bahrain's interior ministry said three Egyptians, three Bahrainis and an American were among the survivors.
Commander Jeff Breslau, a spokesman for the US fifth fleet, told the BBC they had been nearby when the boat capsized. "It happened one mile east of where we're headquartered, so as soon as we got the call we immediately started to move our people and our boats to that area - probably within about 15 or 20 minutes."
US and Bahraini officials said there was no indication the sinking was the result of an attack. "Up to this moment, it appears totally unlikely," the information minister, Mohammed Abdul-Ghaffar Abdullah, told Reuters.
An interior ministry spokesman said the ship's captain, who is not a Bahrani citizen, was being investigated.
