With the cause of the accident a complete mystery, authorities recovered a black box from the Airbus A320 at the crash site, where rescue efforts were being hampered by the mountainous terrain.
Local MP Christophe Castaner, who flew over the crash site, said on Twitter: "Horrendous images in this mountain scenery."
"Nothing is left but debris and bodies. Flying over the crash site with the interior minister -- a horror -- the plane is totally destroyed."
Budget airline Germanwings said the Airbus plunged for eight minutes but French aviation officials said the plane had made no distress call before crashing near the ski resort of Barcelonnette.
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"A black box was found and will be delivered to investigators," Interior Minister Bernard Cazeneuve said.
Weather did not appear to be a factor in the crash, with conditions "calm" at the time.
"There was no cloud at the plane's cruising altitude", winds were "light to moderate" and there was no turbulence that could have contributed to the crash, French weather officials said.
The plane, carrying 144 mainly Spanish and German passengers -- including two babies -- and six crew, was travelling from Barcelona to the western German city of Duesseldorf when it came down.
German authorities said 16 German teenagers on a school trip were on board the doomed plane, as tearful relatives rushed to the airports in the two cities anxiously seeking information about their loved ones.
French President Francois Hollande said he would meet his German and Spanish counterparts at the crash site on Wednesday.