Heavy rains and landslides are hampering the search for survivors of a magnitude 6.9 earthquake that killed at least 63 people and left many others missing in northeastern India, Nepal and the Chinese region of Tibet.

Indian Air Force helicopters made several food drops to villagers late Monday in the mountainous Indian state of Sikkim, the epicenter of the quake, after heavy monsoon rains prevented flights to the area early in the day.

On the ground, rescue workers cleared a major highway leading to the state capital, Gangtok, and restored power to the city. But many villages in remote areas remained unreachable late Monday.

The director-general of India's Indo-Tibet border police, Ranjit Sinha, said that although damage in Gangtok was not extensive, rural areas have been devastated. Local officials said the border police force evacuated 400 people to temporary shelters.

The quake killed at least 35 people in Sikkim and injured more than 100 others. It also caused 13 deaths in the Indian states of Bihar and West Bengal. Many of the victims were killed by collapsing buildings and mudslides.

Nepalese authorities reported eight quake-related deaths, while China's official Xinhua news agency said at least seven people were killed in southern Tibet.

Two strong aftershocks followed Sunday's quake and experts warned that more could follow. Many residents of Gangtok spent Sunday night and Monday morning in the streets, too afraid to stay in their homes.

Indian Prime Minister Manmohan Singh called an emergency meeting on Monday to coordinate the disaster response.