The French government says a fishing boat sank off the French island of Mayotte in the Indian Ocean, leaving two adults and three children dead. Fifteen people are still missing.

The small, motorized vessel was carrying around 40 people, witnesses said. It went down Saturday afternoon after setting off from the African Comoros Islands.

In a statement Sunday, the Overseas Territories Ministry said 19 people were rescued and taken to the hospital in Mayotte's capital, Mamoudzou.

Overseas Minister Victorin Lurel says an air and sea search operation will continue "as long as necessary" to find the missing.

It's not immediately clear what caused the sinking, but the small "kwassa-kwassa" boats are thought ill-equipped for long sea trips.

The 115 kilometer (71.46 mile) stretch to Mayotte is a common route for Comorians who hope to reach the richer French administered island.