Police are questioning the captain of a boat which capsized off the coast of Bahrain, killing at least 57 people.
The boat's owners blamed overcrowding for the disaster, pinning blame on the tour company operating the vessel.
Local prosecutors in Bahrain said the captain was not properly qualified and detained him and his assistant.
Bahraini officials say it is too early to say what caused the boat to overturn, killing mainly foreigners including 21 Indians and 12 Britons.
At least 67 people were rescued from the al-Dana vessel, while two are still missing.
Abdullah al-Qubaisi from the owners, the al-Dana company, said tour operators had insisted on setting sail even though there were too many people on board.
The passengers were mostly foreigners from construction company Nass-Murray and Roberts, who were celebrating completion of part of the Bahrain World Trade Centre towers.
Helicopters and ships have been scouring the area less than a mile from the coast.
Bahraini officials have said those who died were of 16 nationalities, including Egyptians, Filipinos and South Africans.
The boat's captain was detained as an official investigation into the disaster began.
"The prosecutor's office has detained him and his assistant," local official Nawaf Hamza said.
Correspondents and eyewitnesses have reported that the boat appeared heavily overcrowded before it set off into the harbour.
Mr al-Qubaisi told state television it was allowed to carry only 100 passengers.
Officials earlier said that they believed there were 137 on board when the incident occurred, but the figure was then revised to 126.
5 South Africans
1 South Korean
8 South Africans
1 Sri Lankan
He said the boat was rented to a local tour company, which arranged a dinner and cruise for employees of a Bahraini firm.
"They loaded the boat with more than its capacity. The captain refused to sail but they forced him to leave," Mr Qubaisi said.
Bahrain's coastguard chief Yussef al-Ghatim told AFP news agency "the organiser of the trip said 150 people were invited but some 14 to 20 may have gotten off before it sailed".
The boat was hired by Island Tours. The company has been unavailable for comment.
The chief executive of the company holding the party on the boat said their understanding was that the boat may have been capable of taking 200 people.
"We don't know whether there was overcrowding or not," Brian Bruce told the BBC.
The boat capsized at about 2145 local time (1845 GMT), near one of the bridges linking the capital Manama with al-Muharraq island, Mr al-Ghatim said.
An Indian barman who had been onboard told the Gulf Daily News that the boat had "rocked badly and tilted over" after hitting a wave.
"The refrigerator and cooker all slid to one side of the boat and with that extra weight, the boat couldn't sustain it any longer and we rolled," he said.
A Bahraini survivor spoke of the passengers' fear in the water.
"They were fighting with each other and screaming," Khalil Mirza said.
Rescue boats and helicopters were quickly despatched and survivors and victims were pulled from the water throughout the night.
The search mission is continuing in close co-operation with the US navy.
Graphic based on latest information available