The fire that broke out January 28 aboard Air Busan Flight BX391 at Gimhae International Airport is believed to have started due to a short circuit inside a passenger’s battery pack.

The transport ministry’s Aviation and Railway Accident Investigation Board announced the results Friday, based on a detailed analysis by the National Forensic Service.

According to the analysis, multiple electric molten marks were identified on the remains of the battery pack found on board.

This suggests that a dielectric breakdown, which occurs when the positive and negative terminals of a battery short circuit, may have been the initial cause of the fire.

The National Forensic Service added that while the battery was severely damaged, making it difficult to determine the exact reason for the short circuit, it is highly unlikely that the fire originated from a source other than the battery pack.