A portion of the dam built by the Bengal irrigation department on the Atrayee river in Balurghat of South Dinajpur district collapsed on Sunday night, triggering panic among residents on the riverbank.

Early on Monday, the embankment and concrete steps adjacent to the weir dam were also damaged, with parts of them submerging into the river.

Chief minister Mamata Banerjee had inaugurated the dam, built at a cost of ₹32 crore, in January last year. As parts of the structure gave away within a year, questions were raised from various quarters about the quality of the work.

Sources said that the breach occurred around 10pm (Sunday) in ward 13 in Chakbhrigu, a locality on the western side of Balurghat town.

“By 3am (Monday), the sluice gate and iron-reinforced concrete sections of the dam had also collapsed. We spent a sleepless night fearing that our area might get flooded,” said Amal Ghosh, a resident of the area.

As the news spread, Bijin Krishna, the district magistrate of South Dinajpur, and Chinmoy Mittal, the superintendent of police, visited the site along with officials of the state irrigation department to assess the situation.

Krishna said that the dam’s main structure was intact and that some adjoining structures and portions of the embankment collapsed due to erosion.

“The matter has been reported to higher authorities and a central team from the irrigation department will visit the site for further assessment,” he said.

“There is no reason for residents to panic. Workers have been engaged at the site and we expect temporary (repair) work to be finished soon,” the DM added.

Sources said engineers of the irrigation department had started emergency repairwork.

“The administration has assured that the breach at the embankment would be sealed within 24 hours, using sandbags,” said a source.

The Atrayee river, one of the prominent rivers in north Bengal, enters the district from the Dinajpur district of Bangladesh.

In Mohanpur of Dinajpur, Bangladesh has built a dam to control the river’s flow. Chief minister Mamata Banerjee has expressed her grievance many times over the dam and even sought the Centre’s intervention in the matter.

Last, year, this Balurghat dam, which controls the flow of water into the Naogaon district of Bangladesh — after flowing into South Dinajpur, the river enters Bangladesh again — was commissioned to ensure that there was adequate water on the Indian side of the border.

With parts of the dam collapsing, Sukanta Majumdar, the Balurghat MP and a Union minister of state, was quick to blame the state government.

“The project was flawed from the start as the dam was built without consulting experts. The ruling party leaders pocketed commissions and used substandard materials which led to this collapse,” Majumdar alleged.

Biplab Mitra, the state consumer affairs minister who is from the district, reacted, claiming the DM had personally supervised the construction work.

“There was no compromise on quality. The damage may have been caused by the force of water or some other reason. The MP is making baseless accusations,” said Mitra.