The upper reaches of Sikkim experienced heavy snowfall, an official said on Wednesday.
The snowfall on Tuesday evening also led to a sharp dip in temperatures in the Himalayan state.
According to the official black ice has formed at Thulo Khola, making the road to Nathula and Tsomgo Lake dangerous for vehicles.
Efforts are underway to clear the snow but it will take a day or two to ensure safe passage, the official said.
Permits for visiting Nathula and Tsomgo Lake will not be issued by the Tourism department until further notice. Travellers are advised to stay updated on the situation and exercise caution.
The administration is monitoring the weather and road conditions closely, the official added.