Rescue workers are battling damaged roads and landslides to reach areas struck by Sunday's Himalayan earthquake that killed at least 100 people.

The 6.9-magnitude quake was centered in the Indian state of Sikkim and caused damage and fatalities across northeastern India, Nepal and the Chinese region of Tibet.

Sikkim officials said Wednesday there was still no contact with a number of villages in the quake zone and that the death toll my rise further.

A company building a hydroelectric plant in northern Sikkim said at least 17 of its workers had been killed in landslides triggered by the earthquake. Many workers were still unaccounted for.

Army officials say at least 45 tourists, including several foreigners, were rescued by helicopter Wednesday after being stranded in the popular mountain resort of Lachung.

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

Eighteen others were killed in the Indian states of West Bengal and Bihar.

Multiple landslides, fog and heavy rain had prevented many rescue workers from reaching the impact zone. Rescue efforts were in full effect Wednesday after more than 5,000 army troops blasted though rockfalls to clear a major highway leading to Mangan, a town near the epicenter.

Sikkim's Chief Minister Pawan Kumar Chamling said Wednesday that the quake has caused about $21 billion of damage in the state.