A powerful earthquake across the Himalayan region straddling India, Nepal and China killed at least 55 people when it struck Sunday night.
The 6.9 magnitude quake also damaged more than 100,000 homes in the area.
The epicenter was in India's Sikkim state near borders with Nepal and China's Tibet region, but the shaking was felt across northern and eastern India and to the south in Bangladesh.
TV news broadcasts showed footage of buildings buckled, sidewalks cracked and two major roads collapsed in Gangtok, 42 miles southeast of the quake's epicenter.
Rescue workers were trying reach remote villages cut off by the quake to ascertain the damage.
Initial reports say three emergency workers were killed in the frantic, rain-soaked rescue effort.
More than 6,000 troops worked to clear concrete slabs, bricks and mud to rescue scores of people trapped under houses that collapsed.
Nine helicopters dropped food to villages, airlifted a medical team, evacuated the injured and conducted damage assessments, Indian Home Secretary R.K. Singh said. Heavy construction equipment was used to clear some of the blocked roads, he said.
"The rescue and relief operations are in full swing though they were hampered. by poor weather," Singh said.
Since the initial quake, there have been at least two sizable aftershocks. Seismology experts are warning residents that more are possible.