(CNN) All 65 people on board a passenger plane that crashed Sunday in a mountainous region of southern Iran are presumed dead, the airline said.

The Aseman Airlines plane was flying from Tehran to the southwestern city of Yasuj when it disappeared 50 minutes into the flight, according to a post on the airline's Instagram account.

The flight, which departed at 7:55 a.m. local time (11.25 p.m. ET Saturday), crashed in Kohangan village, 120 kilometers (74 miles) from Semirom town, authorities told Iran's Fars News Agency .

Earlier reports said 66 people had died in the crash, but one would-be passenger did not board the flight, Aseman Airlines confirmed Sunday.

Iran's Supreme Leader Ayatollah Ali Khamenei and President Hassan Rouhani expressed their condolences to the victims and their families, ordering officials to spare no efforts in their rescue operation, the state-run Islamic News Agency reported.

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