The New Zealand accident investigator said Chilean authorities had confirmed they had opened a probe into the flight, and it was assisting with their enquiries.

A spokesman for TAIC said because the incident on the Sydney-Auckland flight on Monday occurred in international airspace it fell to Chilean accident investigation authority Direccion General de Aeronautica Civil (DGAC) to open an enquiry.

“TAIC is in the process of gathering evidence relevant to the enquiry, including seizing the cockpit voice and flight data recorders,” the New Zealand agency said, referring to the so-called “black boxes” that will provide more information on the flight’s trajectory and communications between pilots.

The airline and passengers aboard the flight said on Monday the plane with 263 passengers and nine crew members on board dropped abruptly mid-flight.

The cause of the apparent sudden change in the trajectory of the flight is currently unexplained. Safety experts say most airplane accidents are caused by a cocktail of factors that need to be thoroughly investigated.

New Zealand’s Civil Aviation Authority said in a statement it would also assist in the investigation if required.