A boat accident off the coast of northeastern Madagascar on Monday killed at least 83 people, the country’s maritime agency said on Wednesday.

Fifty people have been rescued and five are still missing, a spokesperson for the Maritime and River Port Agency (APMF) told CNN. The boat, which was carrying 138 people, sank late on Monday night, according to the APMF.

The vessel, a cargo ship named “Francia”, was not authorized to transport people, the APMF spokesperson said.

The boat was overloaded and water flooded the engine, APMF’s director of operations at sea Mamy Randrianavony said, according to Reuters.

Searches were put on hold on Wednesday due to bad weather and should resume on Thursday, the APMF said.

Gen. Serge Gelle swam for nearly 12 hours to shore after the search helicopter he was on crashed at sea late on Monday amid efforts to locate survivors of the boat accident, the APMF said.

Gelle, who heads the national Gendarmerie, was found alive Tuesday morning after swimming for nearly 12 hours, the APMF spokesperson told CNN on Wednesday.

Gelle said in a Tuesday statement that the helicopter crashed due to “wind gusts.” He was accompanying Prime Minister Christian Ntsay and the Minister of National Defence Gen. Leon Richard Rakotonirina, who had traveled to the region to oversee the search operations in a separate helicopter.

President Andry Rajoelina applauded their efforts in a tweet on Wednesday, saying that he “commanded their complete devotion” to the task.

The APMF said the helicopter had three other passengers on board when it crashed: A mechanic, a pilot, and Col. Olivier Andrianambinina.

The mechanic was found alive and was rescued on Tuesday, the APMF said. Andrianambinina’s body has been found, while a search is still ongoing for the pilot, it said.

Rajoelina announced a national day of mourning for Thursday. (CNN)