Police arrested one person in connection with the blast at an illegal firecracker factory in West Bengal's North 24 Parganas district in which at least eight people were killed and scores injured, an officer said on Monday.

The arrested person is the partner of the owner of the illegal firecrackers factory, police said.

The situation at Nilgunj's Moshpole within Duttapukur police station limits was calm on Monday.

"Search operations continued the entire night. However, the lack of power in the area and huge amount of debris scattered here made it tough for us to conduct searches and our investigation. We have arrested one person who was the business partner of the man running the unit," a senior police officer of Barasat Police District told PTI over the phone.

The man has been booked under the Explosives Act 1884 and Explosives Rules 2008, the officer said, adding that a suo moto case was started against three others in connection with the blast.

The blast in the illegal firecracker factory took place around 8.30 am on Sunday when people were working in the factory.

The blast's impact was so intense that over 50 houses in the neighbourhood were partially damaged and body parts of people were found on terraces of several buildings.

Police said the owner of the illegal firecrackers factory and his son, who was present in the unit, were also killed in the blast.

Police and local administration employed JCB machines to bring down the remaining part of the building, housing the illegal firecracker unit and clear debris from the area, the police officer said.

Talking about the condition of those injured in the blast undergoing treatment at the Barasat Medical College and Hospital, the police officer said that the condition of one remained "very critical" while others were improving.

Many local people alleged that despite complaining to the police regarding the illegal firecracking unit, no action was taken.

"Now, when so many lives have been lost, what will the police do in arresting people? They should have taken necessary actions when we had complained to them," Ratan Hasan Ali, a local, said.

Twelve people were killed in a similar explosion at an illegal firecracker factory in Purba Medinipur district's Egra in May while three died in another explosion in Maheshtala in South 24 Parganas district.

Soon after the blast, the TMC and BJP engaged in a war of words with the saffron party demanding a NIA probe while the Trinamool asked the BJP to stop doing "vulture politics."

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