The first report on last month’s Jeju Air crash in South Korea has confirmed traces of bird strikes in the plane’s engines, though officials haven’t determined the cause of the accident that killed all but two of the 181 people on board.

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.

A preliminary report has revealed that feathers and bird blood stains were found in both engines of the Jeju Air plane following the horrific crash killed 179 people at Muan International Airport