A 100ft-long embankment protecting Bhutni island in Manichak block of Malda district collapsed on Friday, endangering nearly 20,000 people.

The Ganga which surrounds the island was flowing 0.15 meters above the extreme danger level on Friday evening. The extreme danger lever of the Ganga in the district is 25.3 meters.

Sabina Yeasmin, minister of state, irrigation and waterways department, said: “A long stretch of the main embankment at Manichak block has collapsed. We are keeping a close vigil on the situation.”

Irrigation officials are trying to reinforce the ring embankment — the second line of defence after the main embankment — in the Koshi Ghat area of Bhutni. But local people doubt if the gushing waters can be stopped.

Bhutni island is about 15km from the block headquarter of Manichak, which is among blocks affected worst by the raging river. Malda has 15 blocks.

In Bhutni, villages like Kesharpur, Binpara, Kesharpur Colony are largely inundated as of now.

Pranab Kumar Samanta, executive engineer of the irrigation department, said despite all measures, the main embankment could not be saved. “Our target is to fortify the ring embankment at any cost to avoid further damage,” he said.

It is being anticipated that if the ring embankment collapses, the majority of the localities in Uttar Chandipur and Hiranandapur gram panchayts of Bhutni and the most-densely populated area of the island would be completely inundated. The third gram panchayat on the island is Dakshin Chandipur.

The population of Bhutni is around 1 lakh.

Residents of villages like Gadai Char of Bhutni, which are completely inundated, have started take refugee in higher areas abandoning their houses.

The water levels of two other rivers in the district, Mahananda and Fulhar, are also increasing.

The Mahananda was flowing at 19.75 meters, a little below the danger level, while the Fulhar is flowing in the danger zone at 27.35 meter.