Three British men were on board a passenger plane that crashed in a remote area of northern Afghanistan, the Foreign office has confirmed.
Chris Carter, David Taylor and Daniel Saville were among 44 passengers on the Pamir Airways flight which crashed in a mountainous region of the country.
Search teams, assisted by US and Nato forces, are on their way to the crash site, officials say.
The men's next of kin have been informed, the Foreign Office said.
A Ministry of Defence spokesman confirmed there were no British military personnel on the plane.
The plane is thought to have gone down near the Salang Pass, a mountainous area about 60 miles (100km) north of the capital, Kabul, on Monday morning.
A Nato search plane flew to within four miles (6.5km) of the crash site but had to turn back due to poor weather.
A Nato spokesman said: "All eyes were searching for the plane, but the fog was so bad you couldn't tell where the mountain began and the fog ended."
Snow and floods
General Rajab, commander of the Salang Pass for the Afghan ministry of public works, said: "The weather is very bad. It is snowing. There is flooding."
Col Nabiullah, in charge of the southern portion of the pass, said: "The only way they can search is on foot. The helicopters can't get in."
The Salang Pass is a major route through the Hindu Kush mountains connecting the capital, Kabul, to the north of the country.
Pamir Airways is one of Afghanistan's private carriers and operates mainly domestic routes across the country.
The BBC's Mark Dummett in Kabul says it is too early to predict what might have caused the crash, but added that the bad weather over Kabul and in the surrounding areas was a possible cause.
He said: "The Afghan police have launched a search operation in these mountains.
"Because they haven't been able to find the plane yet, it's all speculation, but [the bad weather] seems the most likely explanation at the moment.
"It won't be until the search teams are able to get to the crash that we will find out more, or that we find out the fate of those people on board."
In 2005 an Afghan airliner crashed in the Band-e-Ghazi area east of Kabul. More than 100 people were killed.