TEHRAN, Iran — A commercial plane crashed on Sunday in a foggy, mountainous region of Iran, killing all 66 people on board, the state news media reported.
The Iran Aseman Airlines plane went down near its destination, the city of Yasuj, about 485 miles south of the capital, Tehran.
Mohammad Taghi Tabatabai, a spokesman for Aseman Airlines, told state television that everyone aboard the ATR-72, a twin-engine turboprop used for short-distance regional flights, had been killed.
It was carrying 60 passengers, including one child, and six crew members, according to The Associated Press.
The cause of the crash was not immediately clear.
The Iranian Red Crescent said it had deployed people to the area, and the authorities said they would be investigating.
The fog prevented rescue helicopters from reaching the site in the Zagros Mountains, state TV reported. Mr. Tabatabai said the plane had crashed into Mount Dena, which has an elevation of about 14,500 feet.
News reports said the plane disappeared from radar screens 50 minutes after taking off from Mehrabad International Airport in western Tehran, which mainly serves domestic flights although it also has some international routes.
Under decades of international sanctions, Iran’s commercial passenger aircraft fleet has aged, with accidents occurring regularly in recent years.
The sanctions have prevented the oil-rich country from updating its fleet, forcing it to use substandard Russian planes and to patch up older jets far past their normal years of service, drawing on spare parts bought with increasing difficulty on the black market. Most Iranian planes, including the 727, are forbidden to operate within the European Union.
In 2014, a locally built Iranian passenger plane crashed shortly after takeoff from Mehrabad airport, killing 39 people and reviving questions about the safety of an aviation sector left hobbled by international sanctions.
The plane was based on a relatively obscure Ukrainian design that had been involved in previous Iranian air disasters. The Sepahan Air regional airliner, bound for Tabas in eastern Iran, went down in a residential area shortly after takeoff at 9:20 a.m.
The Antonov 74 aircraft crashed shortly after takeoff, the director of the airport said. The plane had been headed to Shiraz in the south of Iran.
Earlier that year, a plane carrying 147 passengers caught fire while landing in northeastern Iran, killing 29 of the 148 people on board and injuring 47, state-run television reported.
The plane, a Russian-made Tupolev-154, apparently blew a tire while landing in Mashhad, slipped off the runway and burst into flames, the governor of Khorasan Province said.
After the landmark nuclear deal with world powers in 2015, Iran signed deals with Airbus and Boeing to buy scores of passenger planes.
The ATR 72 involved in the crash on Sunday, a French-Italian short-haul aircraft, was introduced in the late 1980s. The Aseman Airlines fleet’s aircraft were delivered from 1993 to 2009.
Aseman Airlines is a semiprivate carrier based in Tehran that specializes in flights to remote airfields across the country. It also flies internationally.
By THE NEW YORK TIMES