At least ten people died and 80 others, including 22 army personnel, went missing on Wednesday after a cloudburst over Lhonak Lake in north Sikkim triggered a flash flood in the Teesta River basin, officials said.

All 10 who died have been identified as civilians including 3 of the dead who were washed up in north Bengal, they said adding that one of the 23 army men who had gone missing in the morning was rescued later.

The flood in Sikkim that started around 1.30 am was made worse by the release of water from Chungthang dam, the officials said.

Over 3,000 tourists from various parts of the country, were reported to be stranded in different parts of Sikkim, Sikkim Chief Secretary V B Pathak said.

Several workers employed with Teesta Stage III dam in Chungthang were also stranded in tunnels of the dam, Pathak said.

The Sikkim Chief Secretary said that the road infrastructure has suffered extensive damage due to flooding as 14 bridges have collapsed with nine ofthem being under Border Roads Organization (BRO) and five others belonging to the state government.

Scores of people missing and injured have been reported from Chungthang in Mangan district, and Dikchu, Singtam in Gangtok district and Rangpo in Pakyong district, Pathak said.

Another official said some 166 people have so far been rescued, including the army man.

"The health condition of the rescued soldier is stable," Defence Spokesperson Lt Col Mahendra Rawat said.

Bodies, including that of a child, were fished out from the flood plains of the Teesta river at Golitar in Singtam by rescue personnel, the officials said.

Prime Minister Narendra Modi spoke to Chief Minister Prem Singh Tamang on Wednesday to take stock of the situation in the state and assured him of all possible support.

"Spoke to Sikkim CM Shri @PSTamangGolay and took stock of the situation in the wake of the unfortunate natural calamity in parts of the state. Assured all possible support in addressing the challenge. I pray for the safety and well-being of all those affected," Modi said on X.

Defence Minister Rajnath Singh also prayed for the well-being of the missing army personnel.

The Sikkim government, in a notification, said the natural calamity has been declared as a disaster.

The release of water from the Chungthang dam led to a sudden increase in water levels up to 15-20 feet high downstream, the defence spokesperson said.

“Twenty-two army personnel have been reported missing and 41 vehicles submerged under the slush,” he said.

Troops of Trishakti Corps launched a massive search operation to trace the 23 missing soldiers amid heavy rain and rescued one of them in the evening.

"All other Indian Army personnel posted in Sikkim and North Bengal are safe but they are unable to contact their family members due to disruptions of mobile communication," a defence official said.

“A steel bridge at Singtam, known as Indreni bridge, 30 km from the state capital Gangtok has been completely washed away by Teesta river water early Wednesday,” another Sikkim government official said.

Rajeev Bhattacharya, 25, a tourist from Kolkata who was on a trek from Gangtok towards Singtem, told PTI over phone: “We saw a huge wave of water rushing at great speed through the valley and mangled remains of structures being swept away. Luckily, my friends and I were on high ground and not affected by the flash flood. We are now making our way back to Gangtok.” Several towns, including Dikchu, Singtam and Rangpo located in the Teesta basin, have also been flooded with the upsurge in the river.

Meanwhile, all schools located in Mangan, Gangtok, Pakyong and Namchi districts will remain closed till October 8, the education department said.

Parts of National Highway-10, the main link between Sikkim and the rest of the country, were washed away, the officials said, adding, a flood alert has been issued for North Bengal and Bangladesh through which the Teesta flows.

“We were travelling to Gangtok from Siliguri when our car was forced to halt in the Swetjhora area. The NH-10 had caved in as incessant rains had eroded the rock and soil below the road. Fortunately, all cars were moving slowly because of the rains, otherwise, the cave-in could have actually swallowed a vehicle,” Dolma Bhutia, a college student going back home to Sikkim, told PTI.

Police officers in neighbouring West Bengal said two youths from Uttar Dinajpur district - Swarnadwip Majumder (23) and Srikant Majumder (27) and another, Ishan, from Jharkhand - went missing in Sikkim on Wednesday.

The trio had left for the small Himalayan state on Saturday on a motorcycle holiday.

"Since Tuesday morning, they could not be traced as their mobile numbers remained unreachable. We have contacted Sikkim Police for help,” a police officer from Raiganj, the district headquarters town, said.

The officials said two other bridges, Baluatar and another near the Lanco Hydel power project, have collapsed due to the spate in Teesta since Tuesday night.

The administration has set up a number of relief camps, where hundreds are taking shelter, they said.

The Sikkim State Disaster Management Authority stated that a "cloudburst in portions of Lhonak Lake, which caused the rise of water levels with very high velocities downstream along the Teesta River basin in the early hours of Wednesday" damaged many establishments in Mangan, Gangtok, Pakyong, and Namchi.

Chief Minister P S Tamang visited Singtam and took stock of the situation. He also held a meeting with senior officials at the Singtam Nagar Panchayat office and asked them to keep vigil.

In a post on social media, Tamang said his thoughts and prayers are with all during this difficult hour.

“I want to assure you that the government is fully committed to providing all necessary assistance and relief to those in need. We understand the magnitude of the situation and are mobilising all available resources to ensure the safety and well-being of our citizens. Our dedicated teams are working day and night to address the immediate concerns and challenges posed by this calamity,” Tamang said.

Meanwhile, fearing the shortage of ration and other essentials in Sikkim, the state government has decided to construct Bailey bridge with help from the Army and NHIDCL.

The state government has set up 18 relief camps in Singtam, Rangpo, Dikchu and Adarsh Gaon to house the displaced people.

In West Bengal, torrential rain in the last few days, besides an increase in the water level in the Teesta river, affected several places in Kalimpong, Darjeeling, Alipurduar and Jalpaiguri districts, where the administration has started evacuating affected people to safer locations.

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