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.

According to a preliminary investigative report released on Monday, feathers and blood stains on both engines of the Jeju plane came from Baikal Teal, a type of duck that has a large number of flocks.

An investigation into the crash – the deadliest on South Korean soil – will now focus on the role of the bird strike and the concrete structure at the end of the runway where the plane crashed.

The report said the Boeing 737-800’s engines will be removed and the concrete structure will be further inspected.

The Jeju Air plane took off from Bangkok on the morning of December 29 and flew to Muan International Airport in the southwest of the country.

At approximately 08:57 local time, three minutes after the pilot made contact with the airport, the control tower advised the crew to be cautious about “bird activity.”

The pilot reported at 08:59 that the aircraft had struck a bird, announcing the Mayday signal.

The pilot then requested permission to land from the opposite direction, during which it belly-footed without the landing gear deployed. It covered the runway and exploded after hitting a concrete structure, reports said.

Authorities earlier said plane data and cockpit voice recorders were taken from the plane Stop recording About four minutes before disaster struck.

Experts who flew the same type of aircraft involved in the crash also questioned the presence of concrete barriers along the runway – some suggesting that if there were no casualties, their toll would be lower if they were not there.

The concrete structure houses a navigation system that helps aircraft land (called locals).

South Korea’s Transport Ministry said the system could also be found at other airports in the country and even overseas.

Last week, authorities announced they would Change concrete barriers used for navigation at seven airports across the country. Following the review, seven airports will also make adjustments to their runway safety areas.

Preliminary reports have been submitted to the United Nations Aviation Administration and authorities in the United States, France and Thailand.