Authorities have suggested that migratory bird strikes were the cause of last month's deadly plane crash in South Korea, according to multiple reports.

The feathers and blood stains on both engines of the Jeju Air plane were from the Baikal teal, a type of migratory duck that flies in large flocks, according to a preliminary investigation report published on Monday.

The exact cause of the Jeju Air crash remains unclear, and the investigation is complicated because the black boxes stopped recording four minutes before impact.