Officials investigating a jetliner crash that killed all 46 people aboard, including seven Americans, say it could be several months before the cause of the disaster is fully known.

Officials Thursday cited pilot error and technical failure as possible causes of the Wednesday night crash as the Alitalia DC-9 approached Zurich international airport en route from Milan, Italy.Radar data showed the plane was flying about 990 feet too low, Alitalia and Swiss officials said there was no explanation yet for the low altitude.