Three persons died and 23 army personnel were washed away on Wednesday after a cloudburst over Lhonak Lake in north Sikkim resulted in a flash flood in the Teesta River basin, which was aggravated by the release of water from a dam, officials said.

The flood started around 1.30 am, they said.

"Three bodies have been recovered from Singtam during rescue and relief efforts," a Sikkim State Disaster Management Authority official said.

The SSDMA, in a press release, 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 districts.

All schools located in the four districts of Sikkim will remain closed till October 8, the education department said in a circular.

Defence officials said establishments along the Lachen valley have been affected and efforts are on to confirm details.

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

This has led to army vehicles parked at Bardang near Singtam getting affected, Defence spokesperson Lt. Col Mahendra Rawat said.

Twenty-three army personnel have been reported missing and 41 vehicles submerged under the slush, he said, adding that search operations are underway.

Border Road Organisation (BRO) has already launched rescue operations and 80 locals have been safely evacuated so far, the Defence officials said.

A steel bridge at Singtam, also known as Indreni bridge, in Gangtok district has been completely washed away by Teesta river water early on Wednesday.

The 120-metre-cable suspension bridge is an important thoroughfare.

"All the affected people of Singtam town have been taken to safe places and residents of Dikchu village along the river belt have been evacuated to a nearby school," a Sikkim government official said.

The water level increased drastically overnight, affecting the dam site of the NHPC hydroelectric power project near Dikchu village, he said.

Chief Minister PS Tamang visited Singtam and took stock of the situation arising out of the flash flood in the Teesta River basin.

The CM held a meeting with senior officials at the Singtam Nagar Panchayat office and asked them to keep vigil.

In a statement, the chief minister said his thoughts and prayers are with all during this difficult hour.

“In these challenging times, I want to extend my heartfelt support to all the victims and their families affected by this unfortunate event,” Tamang said.

“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 mobilizing 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,” he said in a Facebook post.