Updated

Rescue workers labored in bitter cold and fierce winds Thursday, digging out nearly 300 people trapped in their cars and a tunnel by a snow avalanche in the soaring Hindu Kush mountains. Four people were killed, officials said.

Three of the dead suffocated inside the Salang Tunnel, and the fourth died in a car buried by snow outside as temperatures overnight plunged to minus 40 degrees, said U.N. spokesman Yusuf Hassan.

Rescuers battling winds up to 55 mph managed to reach all 57 cars buried outside the tunnel by Wednesday's avalanche and pulled out around 100 people, Hassan said.

About 190 people trapped inside the tunnel were also freed, said Mohammedullah Gulaga, the Afghan coordinator of the rescue effort.

The rescue teams included U.S. soldiers and workers from HALO Trust, an international mine-clearing organization active in the area.

Some 50 to 60 people were treated at a field clinic at Jabal Saraj, between Kabul and the tunnel, said Paul Barnard, a spokesman for the international peacekeeping force in Kabul. Hassan said most were suffering from frostbite and dehydration.

Salang tunnel, 80 miles north of the capital, lies on the main road crossing the Hindu Kush and connecting Kabul to northern Afghanistan. It is the main route for aid shipments from north to south. The two-mile-long tunnel, a widely admired engineering, feat was damaged in Afghanistan's wars but reopened in January after Russian-led repairs.

Substantial snowfalls in recent days in Kabul and some other parts of the country have raised hopes that Afghanistan is seeing the end of a three-year drought that has aggravated the devastation of war.

But the snow also has blocked aid from reaching some remote regions, underlining how the country's severe terrain and primitive infrastructure complicate the interim government's efforts to lead the country toward stability and security.