The rescue operations have been hampered by heavy rain, thick clouds and landslides.
Rescue workers with sensors and sniffer dogs searched through the rubble on Wednesday for more survivors of the earthquake that has killed at least 92 people in a remote Himalayan region spanning India, Nepal and the Chinese region of Tibet.
More than 3,000 people have been rescued in the Sikkim, the epicentre of the 6.9 magnitude quake, since Sunday in operations hampered by heavy rain, thick clouds and landslides that cut off some of the worst affected areas.
Remote areas near the state's northern border with Tibet remain out of reach as rain washed away roads that are now being hastily rebuilt by hundreds of construction workers. About 45 tourists are among those holed up in the area, while workers at a hydroelectric plant remain unaccounted for.
"The death toll is likely to go up," S.K. Pradhan, a senior bureaucrat stationed in north Sikkim, told Reuters. "I think it will take a long time to restore the road communications in some areas."
The quake, which was felt as far away as New Delhi in India and Bangladesh, killed at least 78 people in India alone. In Tibet at least seven died and seven more were killed in Nepal.
Ruling Congress party heavyweight Rahul Gandhi, seen by his supporters as India's next prime minister, touched down on Wednesday in an air force helicopter in Gangtok to meet some of the victims.
Rescue workers are trying to airlift survivors out of the worst affected areas and distribute food and medical supplies in the country's least populous state of 600,000 people. Sikkim is poorly connected by road and has no airport.
"In Gangtok, a few buildings have collapsed and larger buildings like the secretariat and some shopping malls have been sealed as they have developed cracks," Deepak Pradhan, a resident of the state capital told Reuters by phone.
"The roads have opened, but a lot of these landslides have occurred due to poor maintenance." The state's economy boomed in recent years as it opened up to tourism and trade with China. Residents say landslides are a threat to hastily built new buildings in its mountain towns.
For centuries a rarely visited Buddhist kingdom known for the world's third highest peak on its border with Nepal called Kangchenjunga and glacial lakes, Sikkim joined India in 1975. With 600,000 residents, it is the least populated state and borders Bhutan, Tibet in China and Nepal.
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