At least 3 dead in Afghan avalanche

KABUL, Afghanistan (CNN) -- At least three people were killed and more than 20 others may be missing in a snow avalanche in Afghanistan that cut off one end of a key mountain tunnel, according to an official of the International Committee of the Red Cross (ICRC).

The dead included two elderly men and a child. All were believed to have died from carbon monoxide poisoning as a result of people running the engines of their vehicles in the tunnel to keep warm.

The avalanche happened Wednesday amid heavy snow and winds. Michael Kleiner, spokesman for the ICRC in Kabul, told CNN his organization was informed of the deaths Thursday morning.

The avalanche blocked the southern end of the Salang Tunnel, about 80 miles north of Kabul.

Kleiner said the French non-governmental organization ACTED removed three bodies from the tunnel. ACTED is a French NGO specializing in technical support and engineering.

Kleiner said the ICRC received information that vehicles trapped in the tunnel were continuing to run their engines for the occupants to stay warm.

The Halo Trust, a mine-clearing group, told CNN it had rescued 45 people from the avalanche site and was treating them at an emergency first aid center it has set up at Jabal Saraj, south of the Salang Tunnel. As many as 200 additional people, however, may still be stranded in the tunnel.

Rescue attempts have been hampered by drifting snow and high winds. In addition to the vehicles trapped in the tunnel, as many as 30 vehicles are believed covered in snow banks caused by the blowing snow.

Poor roads in combination with the bad weather have hampered convoys of rescue workers and heavy equipment trying to get to the scene.

Several helicopters due to depart at first light Thursday morning remained grounded because of the weather.

The Salang Tunnel was built by the Soviet Union when it occupied Afghanistan in the 1980s. The tunnel is about three miles long and is a major supply route between the north and south of Afghanistan. It had not been used in recent years because of war and land mines but was reopened last month.

-- CNN Correspondents John Raedler and Michael Holmes contributed to this report.