Three people have died and 23 Indian Army personnel were washed away after a cloudburst over Lhonak Lake in north Sikkim resulted in a flash flood in the Teesta River basin on Wednesday.

“Three bodies have been recovered from Singtam during rescue and relief efforts,” a Sikkim State Disaster Management Authority (SSDMA) official said.

The flood started around 1.30 am, officials said.

What are cloudbursts?

Cloudbursts are especially common in mountainous areas and are sudden, very heavy rainfall that are usually local in nature and are of brief duration.

How do cloudbursts occur?

Cloudbursts occur only via orographic lift – a situation when a warm air parcel mixes with cooler air, resulting in sudden condensation.

20 people missing in Pakyong District

As many as 20 people are missing, said Pakyong District Magistrate Tashi Chopel, adding that a lot of buildings and vehicles have been damaged by slush.

“We have opened five relief camps in the district. 3,000-4,000 people were evacuated last night in and around Rangpo,” said Chopel.

The SSDMA said in the early hours of Wednesday the Teesta River basin witnessed rise in water level with very high velocities downstream following a cloudburst in portions of Lhonak Lake.

Several establishments in Mangan, Gangtok, Pakyong, and Namchi districts have been damaged.

Steel bridge at Singtam washed away

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.

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.

As many as 41 vehicles submerged under the slush, Rawat said, adding that search operations are underway.

All schools in the four districts of Sikkim have been ordered by the state education department to remain closed till 8 October.

With inputs from agencies