The setback offset the earlier good news that Canada's navy had said it was confident it had detected the signal from the aircraft's second black box.
Vic Gerden, the chief crash investigator, said the data recording stopped once the plane dipped below 10,000 feet. He said it was a strong possibility that the plane lost electrical power at that stage.
However, he said the flight-data recorder was in good condition and should provide more than 100 types of information ranging from altitude and airspeed to whether the plane's smoke warning lights were on.
The latest developments come amid signs that the disaster befalling the Swiss national airline has reopened wounds between the country's francophone western part and the Swiss-Germans in the east.
An editorial in Le Matin, a popular western Swiss daily, at the weekend called one Swissair director a "snotty little boss, an operetta colonel". The newspaper claimed Philippe Bruggisser ignored French- speaking sensitivities when he favoured German language media while organising a simulation of the effect of smoke in an aircraft cockpit - thought to be one of the origins of the emergency that struck the New York to Geneva flight. The paper also accused Mr Bruggisser of speaking exclusively in Swiss- German and English during press conferences.
The paper criticised the airline's decision to organise memorial services in Zurich, Geneva and New York next Friday as an attempt to undermine another service held in French-speaking Geneva's cathedral.
The comments betray the resentment of the national airline in western Swiss media, which regard Swissair as the epitome of Germanic economic dominance and arrogance. The airline's headquarters are in Zurich, with management dominated by Swiss-Germans.
In April 1996, Franco- phones reacted with fury when Swissair decided to centre all its intercontinental flights on Zurich as part of a cost-cutting drive. Geneva was left with a few European destinations, the New York flight and a new shuttle service to Zurich for connecting flights. It was regarded as a betrayal in the western city, which relies on a wide range of air links to attract international organisations.Reuse content