Iranian rescue teams were still trying to locate the wreckage of a plane on Monday a day after it crashed with 65 people on board, as glacial temperatures and mountainous terrain hampered their search.
The Aseman Airlines flight from Tehran disappeared from radar screens on Sunday 50 minutes into its journey to the southwestern city of Yasuj.
It is believed to have gone down in a mountainous area near the town of Semirom.
Helicopters and mountain rescue personnel from the armed forces and the Red Crescent, as well as local volunteers, were involved in the search, although no one was expected to have survived the crash, state television reported.
“Five units started the search operation in early hours of the morning, in -16 degrees (Celsius, 3.2 degrees Fahrenheit),” a local Red Crescent official was quoted as saying by IRNA news agency.
Military reconnaissance drones were also searching the area.
“We are facing a total enigma. We do not know anything about the crash,” Transport Minister Abbas Akhoundi was quoted as saying by Tasnim news agency shortly after his arrival in Semirom.
Iran has asked European countries and China to help the search operation with their satellite imagery, the deputy head of the Iranian Space Agency, Mojtaba Saradeghi, was quoted as saying by ISNA news agency.
The twin-engined turboprop ATR 72 was just over 24 years old.
According to data cited by the Flight Safety Foundation’s aviation-safety.net website, it had been restored to service just three months ago after being in storage for six years.
Planemaker ATR said the cause of the accident was not yet known.
Based in the French city of Toulouse, ATR is a joint venture between Airbus (AIR.PA) and Italy’s Leonardo (LDOF.MI).
Iran has suffered several plane crashes in the past few decades.
Tehran blames U.S. sanctions for preventing it from importing new aircraft or spare parts.
A deal with world powers on Iran’s nuclear programme has lifted some of those sanctions, opening the way for Iranian airlines to update their fleets.
Aseman signed a deal last year to buy at least 30 Boeing (BA.N) 737 MAX jets.
National carrier Iran Air, has ordered 80 planes from Boeing and 100 from Airbus.
A Boeing 727 plane crashed in northwestern Iran in 2011, killing 78 people, and a Caspian Airlines Tupolev bound for Armenia crashed in 2009, killing 168.
In February 2003, an Ilyushin-76 troop carrier crashed in southeast Iran, killing all 276 Revolutionary Guard soldiers and crew.