A cleaning staff member was killed in the early hours of Wednesday December 23 when a mysterious bomb explosion caused damage at Istanbul’s Sabiha Gökçen Airport while another was wounded. Details regarding the bomb explosion at 2 a.m. are still being investigated and the cause of the explosion remains undetermined, according to a written statement issued by Pegasus Airlines.

The bomb exploded near the area where two janitors were cleaning inside a Pegasus aircraft. One died, while the other was rushed to the Marmara Education and Research Hospital for emergency treatment.

There were no passengers inside the boarding bridge or the plane, however some witnesses claim to have heard three consecutive explosions.

Istanbul Sabiha Gökçen International Airport Investment Development and Operation released a statement noting that there was an ongoing investigation taking place, however there were no problems in take-offs or landings at the terminal so flights would continue smoothly.