Severe weather continued Tuesday to complicate rescue efforts near the remote epicenter of an earthquake that has so far left at least 79 people dead in northeastern India, Nepal and the Chinese region of Tibet.

The magnitude 6.9 earthquake struck Sunday in the sparsely-populated, mountainous Indian state of Sikkim – a region popular with tourists for its Buddhist monasteries and adventure hiking.

Multiple landslides prevented many rescue workers from reaching the impact zone on Tuesday. However, officials say helicopters were able to deliver food aid to Sikkim, despite continued torrential rains and heavy fog.

More than 5,000 army troops are working to clear a major highway leading to the state capital, Gangtok, and restore power to the city.

Most of the deaths from the quake occurred in Sikkim and the rest were killed in the Indian states of Bihar and West Bengal. Many of the victims were killed by collapsing buildings that had already been weakened by heavy monsoon rains.

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

Officials say the death toll is expected to rise.