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

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.

Investigators say they have found evidence of a bird strike on a passenger plane that crashed in South Korea in December and killed 179 people. The feathers and blood stains on both engines of the Jeju Air plane were from the Baikal teal,