Two crew members from Spain and France are feared dead after a Swedish-registered freight jet crashed in a mountainous area near the Norwegian border in Arctic Sweden.

Dag Mejdell, CEO of the Norwegian postal service, says debris has been spotted near the Akkajaure reservoir in Sweden's sparsely populated Lapland region. The postal service had hired the Canadair CRJ 200 aircraft to fly mail to northern Norway.

A mayday message was sent out late Thursday near Akkajaure after which contact with the jet was lost. The cause of the crash wasn't immediately known.

Mejdell said Friday it was "a very serious and tragic accident."

Aircraft-owner West Atlantic Sweden AB said the 42-year-old Spanish captain and the 34-year-old French co-pilot had worked for the company since 2011 and 2008, respectively.