South Korean officials are launching an investigation into the cause of the fire that engulfed an Air Busan passenger plane, with eyewitness accounts suggesting a power bank may have sparked the blaze.

Shares of Air Busan dropped on Friday, after a plane belonging to the budget carrier caught fire earlier this week. Air Busan shares traded down 3.8% as of 0018 GMT, after falling as much as 6.1% to 2,

Concerns have been raised about the safety risk of bringing portable batteries in carry-on luggage for flights, as a lithium-ion battery is suspected as the cause of the fire that destroyed Air Busan’s passenger plane on Tuesday night.