At least 30 people died after their boat sank off the Indian Ocean archipelago of Comoros, a rescue official said on Tuesday.
"At the moment the death toll stands at 30 and 50 survivors," Mouigni Daho, the head of the centre for rescue operations and civilian protection, told AFP.
The accident occurred Monday night to the south of the Comoros' main island of Grande Comore where the boat had left for the archipelago's other island of Anjouan.
Red Crescent rescue coordinator Arfachad Salim said the death toll could increase.
"We cannot rule out that passengers are still trapped inside the boat," said Salim, who earlier said they estimated that more than 100 people were in the boat.
It was not immediately clear what caused the accident, although Salim said overloading could be responsible.
Boat accidents are common in the tiny archipelago, especially those carrying migrants from the impoverished isles to the French island of Mayotte.
Geographically, Comoros is made up of four islands of Grande Comore, Anjouan, Moheli and Mayotte. But Mayotte voted to remain part of the islands' colonial master France and is economically better off than its neighbours.