More than 190 bodies have now been recovered in Tanzania after an overloaded ferry sank between the islands of Pemba and Zanzibar.
A government spokesman said 620 survivors had been rescued. Three days of mourning have been declared.
The MV Spice Islander is thought to have capsized after losing engine power.
The BBC reports rescue efforts were hampered by the fact that the overloaded ship capsized at night.
The ferry was bringing people back from holiday after Ramadan and stopped earlier in Tanzania's commercial capital, Dar es Salaam.
About 800 people were aboard the vessel which was licensed to carry a maximum of 600 people.
The Zanzibar government has asked for help from South Africa and Kenya.
The ferry left Unguja at around 9pm on Friday and is reported to have sunk at around 1am on Saturday.
It was reportedly listing before it even sailed. Survivors say some passengers tried to get off, but most were prevented from doing so.
Zanzibar police commissioner Mussar Hamis said survivors were ferried by fast ferries to the main harbour in Stone Town.
Helicopter pilot Captain Neels van Eijk flew over the disaster area.
''We found the survivors holding on to mattresses and fridges and anything that could float,'' he told the BBC.
''By then, there were a few boats that had made their way out.
''They were looking for survivors, but although the sea wasn't so rough, the waves were high so it was difficult for them to spot them.
''We flew to the boats and guided them to the survivors so that they could pick them up. There were also quite a few bodies in the water.''
Tanzania's worst maritime disaster was in May 1996 on Lake Victoria when MV Bukoba ferry sank with as many as 1000 people on board.
Only 114 passengers survived. The captain and eight officials later were charged with the murders of 615 people.