South Korea’s authorities investigating last month’s Jeju Air plane crash have submitted a preliminary accident report to the UN aviation agency and to the authorities of the United States, France and Thailand,

Bird feathers and bloodstains were found in both engines of the Jeju Air plane that crashed in December, according to a preliminary investigation released on Monday. The Boeing 737-800 was flying from Thailand to Muan in South Korea on December 29 when it crash-landed and exploded into a fireball after slamming into a concrete barrier.

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,