At least 100 Bangladeshi fishermen died in the Bay of Bengal after a fierce storm struck dozens of fishing boats, authorities confirmed Sunday.

The fishermen were aboard at least 15 boats which sank when an unexpected storm brought powerful winds and huge waves two days ago. Several coastal areas in southern Bangladesh were flooded and authorities advised all ships in the Bay of Bengal to remain in shelters until the storm blows over.

Dozens of fishing boats were damaged by the rough waves, but several fishermen managed to swim to shore, authorities in the port city of Barguna said.

On Friday, media said nearly 1,000 persons have been reported missing after the storm pummeled the Bay of Bengal. Dozens of ships were also missing in the huge waves that hampered rescue efforts.

Most of the fishermen reported missing have returned to their homes after swimming to shore or being rescued by other vessels, but approximately 100 weren’t found by the coast guard boats.

They were caught by surprise by the storm after going out to sea at the advent of the autumn fishing season. Survivors described the fierce storm, saying the small fishing boats had flimsy chances to overcome the strong waves and raging winds.

Numerous boats capsized and several went down in the turbulent sea, witnesses said. Divers from the coast guard are trying to find the missing people, but the turbulent sea hampers their activity.