At least 64 people have died in a boat accident off the coast of northeastern Madagascar and searches were underway for 24 missing passengers, the maritime agency said on Wednesday.

Fifty survivors were found, the Maritime and River Port Agency said.

The vessel, a cargo ship that was not authorized to transport people, was overloaded and water flooded the engine, said Mamy Randrianavony, director of operations at sea at the Maritime and River Port Agency (APMF).

It sank late on Monday night with 138 people onboard, APMF said.