The pilot of a terrifying flight from Australia to New Zealand told those on board he temporarily lost control of his Boeing 787 after one of its instruments failed, a passenger said Monday, as authorities investigate what caused a sudden drop that threw travelers around the cabin, injuring dozens.

In accordance with rules outlined by the International Civil Aviation Organization (ICAO), Chile’s Directorate General of Civil Aeronautics (DGAC) have sent investigators from the agency’s Operations and Airworthiness team to look into the incident, according to a statement released on Tuesday.