Authorities in India's earthquake-hit northeast say landslides and heavy rain are hampering efforts by rescue workers to reach survivors of a quake that killed at least 56 people in India and neighboring states.

Rescue workers in India's mountainous Sikkim state found roads blocked by landslides triggered by the magnitude 6.9 earthquake that hit the region Sunday. The emergency personnel were trying to clear the roads to reach villages cut off by the disaster. Indian authorities also tried to airlift rescue and relief teams to affected areas, but low cloud cover prevented helicopters from flying.

The epicenter of the quake was about 60 kilometers northwest of Sikkim's capital, Gangtok, near the Indian border with Nepal. Indian authorities say the quake killed at least 31 people in Sikkim and 11 others in the Indian states of Bihar and West Bengal. Many of the victims were killed by collapsing buildings.

The earthquake also rattled Nepal and the Chinese region of Tibet, which border Sikkim. Nepalese authorities reported seven quake-related deaths, including three people killed by the collapse of a perimeter wall at the British embassy in Kathmandu. China's official Xinhua news agency says at least seven people were killed in southern Tibet.

The quake was followed by at least two strong aftershocks 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. Parts of Sikkim state remained without electricity.