CAIRO — A piece of luggage adrift in the Mediterranean Sea. Floating nearby, a passenger seat from a plane. Scraps of metal, scattered personal belongings and, finally, the grim discovery of human remains.

As the investigation continued Friday into what caused an EgyptAir flight from Paris to Cairo to suddenly and violently plunge from the sky, the discovery of the debris allowed search crews to home in on the location of the crash — an area about 180 miles north of Alexandria, Egypt — even as its cause remained a mystery and the subject of intense speculation.

Data that was transmitted from the aircraft to operators on the ground, published Friday by a respected aviation journal, revealed a rapid loss of control, with alarms and computer-system failures in the seconds before the plane was lost from radar.

The transmissions are evidence of a catastrophic failure, but do not answer the crucial question: What caused it? Why would a plane with a good safety record and experienced pilots fall from the sky on a clear spring night?