What happened
Following landing, the flight crew initiated the start sequence for the airplane's auxiliary power unit (APU) while the aircraft remained on the ramp. Approximately thirty seconds into the operation, smoke began to accumulate within the cabin interior. In response to the developing situation, the captain directed an immediate emergency evacuation. The crew deployed all four evacuation slides, which operated as designed. During the egress process, one passenger sustained a fractured bone in her right foot.
The investigation
A thorough examination of the aircraft was conducted to determine the source of the smoke. Investigators identified a broken hydraulic line within the vicinity of the APU inlet. This failure allowed hydraulic fluid to leak and accumulate in the area surrounding the APU intake, leading to the observed cabin contamination.