INTERPOL and Swiss police are studying CCTV footage of the last sighting of the missing Scots academic Fergus McInnes.
The 51-year-old Edinburgh University research fellow failed to appear at a convention last week, the day after he flew out from the Scottish capital on September 9, and did not check in to his hotel.
Police Scotland said footage shows Mr McInnes at Geneva Airport and boarding a train bound for Martigny where the conference was held.
There has been no sightings of Mr McInnes since he was caught on CCTV after he landed in Switzerland.
Friends believe he may have gone hill walking.
Mr McInnes, a member of the Meadows Croquet Club who lives at St Leonard's Bank, was reported to have visited his sister Lorna, 41, in Blairgowrie, Perthshire, two days before he took the flight.
She said: "He seemed very upbeat."
An appeal for help on Facebook by friends says: "If he did go into the mountains, he might have got lost, or had an accident of some sort.
"For the meantime we keep hoping for a positive outcome."
A Police Scotland spokesman said the search is ongoing and officers have been liaising closely with Mr McInnes' family.
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