The cloudburst occurred over Lhonak Lake in the state's north region.
A cloudburst in Sikkim triggered a massive flash flood on Wednesday leading to the Teesta river flowing at the danger mark. The swollen river waters also washed away parts of the Teesta Dam at Chungthang, the biggest hydropower project in Sikkim.
Visuals from the spot show large portions of the dam's wall missing as the rising Teesta water flowed through it unabated in North Sikkin's Mangan district. The cloudburst occurred over Lhonak Lake in the state's north, leading to the flooding of the river which flows through Sikkim and West Bengal.
As per the Indian Army, the water flowing through the Chungthang dam led to a sudden increase of 15-20 feet in water level downstream. The raging river water also swept away sections of the National highway (NH-10) in Melli, a border town of Sikkim-West Bengal.
Connectivity to Sikkim, including capital Gangtok, has also been affected. Roads in Gangtok, Pakyong, Mangan, Namchi, Gyalshing and Soreng districts have been blocked, Sikkim police said in a report. Portions of NH-10 near Siliguri have also been blocked.
Currently, the Teesta River is flowing at the "danger level" mark of 298.4 metres in the Khanitar district of East Sikkim, as per the Central Water Commission. The water level in West Bengal's Jalpaiguri was recorded as "severe" at 85.95 metres.
Residents in the low-lying areas of Chungthang town and Singtam district in North Sikkim have been evacuated.
"No lives have been lost but there has been significant damage to public property. Some people have also been reported missing. Relief operations are going on," Chief Minister Prem Singh Tamang said while on a visit to Singtam.