A passenger plane carrying 44 people on an internal flight between Kunduz and Kabul has crashed in a mountainous area of northern Afghanistan.
The Russian-made AN-24 aircraft, which had 38 passengers and six crew members on board, crashed in remote mountains between the two cities on Monday, officials said.
"A passenger plane belonging to Pamir Airways with 38 passengers and six crew on board took off today from Kunduz province around 08.30 and was in touch with Kabul airport until 09.10," Mohammadullah Bataz, the acting transport minister, said as he visited the suspected crash site.
"We think the plane has crashed somewhere in this area, in Salang Pass."
According to the passenger manifest at least six of the passengers were foreign nationals, including three Britons, the AFP news agency reported.
Zemarai Bashary, an interior ministry spokesman, said the Nato force in Afghanistan had been asked to assist in the search for the plane. A Nato spokesman confirmed that aircraft had been sent to the area.
"A manned Isaf [International Security Assistance Force] fixed-wing aircraft has been dispatched to the last known position of the missing plane. However, the poor weather conditions in the area are hampering the aerial search," Nato said.
"We cannot rule out any of the usual causes behind crashes; which could be bad weather, technical error, thunder and lightning or even terrorist attacks"
Afghanistan's acting transport minister
"Two Isaf helicopters are en route to the area. Other Isaf helicopters are also on standby ... to assist in any rescue effort."
Bad weather was hampering rescue efforts, Al Jazeera's Hoda Abdel-Hamid, reporting from Kabul, said after speaking to police in the area where the plane is thought to have crashed.
"The conditions are bad. It's so foggy there is no rescue going on," she said.
Seventy rescue workers were searching on the ground on foot as dense fog covered the area of the crash near the 3,800 metre-high Salang Pass.
"The only way they can search is on foot," Colonel Nabiullah, who is in charge of the southern portion of the Salang Pass, said. "The helicopters can't get in."
The acting transport minister said the cause of the accident was not yet known.
"We have to recover the black box to determine the cause," Bataz said.
"We cannot rule out any of the usual causes behind crashes; which could be bad weather, technical error, thunder and lightning or even terrorist attacks."
Other officials blamed the weather for the crash.
Pamir Airways is one of three major private airlines that operate mostly domestic routes across Afghanistan.