More than 400 people in Tibet trapped by a deadly earthquake in the foothills of the Himalayas have been rescued, Chinese officials said on Wednesday, but an unknown number remained unaccounted for in severely cold weather.

The epicenter of Tuesday's magnitude 6.8 quake, one of the region's most powerful tremors in recent years, was located in Tingri in China's Tibet, about 80 km (50 miles) north of Mount Everest, the world's highest mountain. It also shook buildings in neighboring Nepal, Bhutan and India.

Twenty-four hours after the temblor struck, anyone still trapped under rubble would have endured a night in sub-zero temperatures, adding to the pressure on rescuers looking for survivors in an area the size of Cambodia.