The investigation into the deadliest air disaster on the country's soil remains ongoing, focusing on the role of bird strike and involving an analysis of the engines and the "localizer" landing guidance structure.

The preliminary report was released by the Aviation and Railway Accident Investigation Board on Monday in South Korea.

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

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Pilots’ actions after the bird strike are an early focus of the investigation, according to people familiar with the probe.

South Korean officials investigating the fatal Jeju Air crash have published a preliminary report of the accident.

The feathers and blood stains on both engines of the Jeju Air plane were from the Baikal teal, a type of migratory duck that files 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.