A body was found in the wheel well of United Airlines Flight 202, which left Chicago for Hawaii on Dec. 24, the airline said.

At this time, it is not clear how or when the person accessed the wheel well,” the airline said, noting it is working with law enforcement on the incident.

A plane wheel well is a compartment in the wings or fuselage where the landing gear is stored when not in use. It is a hazardous location for stowaways, who could encounter low oxygen levels, hypothermia, crushing, or the risk of falling during the flight.