An Iranian commercial plane has crashed in a foggy, mountainous region of southern Iran, killing all 66 people on board, state media reported.

An Aseman Airlines ATR-72, a twin-engine turboprop used for short-distance regional flying, went down near its destination of the southern Iranian city of Yasuj, some 485 miles south of the Iranian capital, Tehran.

Aseman Airlines spokesman Mohammad Taghi Tabatabai told state TV that all on Flight No. EP3704 were killed.

“After searching the area, we learned that unfortunately … our dear passengers had lost their lives,” Mr Tabatabai said. “This plane had 60 passengers, 59 adults and one child, as well as a pilot, a co-pilot, two flight attendants and two air marshals on board.”

Due to foggy conditions, rescue helicopters could not reach the crash site in the Zagros Mountains, state TV reported. Mr Tabatabai said the plane crashed into Mount Dena, which is about 4,400 meters (14,435 feet) tall.

Aseman Airlines, owned by Iran’s civil service pension foundation, is a semi-private air carrier headquartered in Tehran that specialises in flights to remote airfields across the country. It also flies internationally. It is Iran’s third-largest airline by fleet size, behind state carrier Iran Air and Mahan Air. However, Aseman Airlines is banned from flying in the European Union over safety concerns.

The carrier has a fleet of 29 aircraft, including six ATR aircraft, according to FlightRadar24, a plane-tracking website. The ATR-72 that crashed had been built in 1993, Aseman Airlines CEO Ali Abedzadeh told state TV.

The plane took off from Tehran at 0433 GMT and gave its last signal at 0555 GMT, when the flight was at 16,975 feet and was descending, FlightRadar24 said.

Aseman Airlines has suffered other major crashes with deaths. In October 1994, a twin-propeller Fokker F-28 1,000 commuter plane flown by the airline crashed near Natanz, 180 miles south of Tehran, also killing 66 people on board. An Aseman Airlines chartered flight in August 2008, flown by an Itek Air Boeing 737, crashed in Kyrgyzstan, killing 74 people.

The Iranian Red Crescent said it has deployed to the area. Authorities said they would be investigating. Locals described hearing the crash, though no one had found the crash site yet, according to state TV.

European airplane manufacturer ATR, a Toulouse, France-based partnership of Airbus and Italy’s Leonardo SpA, said it had no immediate information about the crash. The manufacturer specialises in regional turboprop aircraft of 90 seats or fewer.

Under decades of international sanctions, Iran’s commercial passenger aircraft fleet has aged, with air accidents occurring regularly in recent years.

Following the 2015 landmark nuclear deal with world powers, Iran signed deals with both Airbus and Boeing to buy scores of passenger planes worth tens of billions of dollars.

US politicians have expressed concern about the airplane sales to Iran. US President Donald Trump remains sceptical of the atomic accord overall and has refused to re-certify it, putting the deal in question.