The police, however, claimed it to be a cracker burst asserting that no one was injured in the incident.
"It was not an explosion but an unexploded cracker that went off due to the excessive heat. The entire area is cordoned off and over 150 police personnel guard it 24 hours. There is no chance of anyone getting injured," Superintendent of Police (West Midnapore) Bharati Ghosh told IANS.
Twelve people including nine minors were killed and four injured when an explosion ripped through the cracker factory in Pingla in the district on May 6.
A team of rights activists, visiting the area, claimed the blast was loud and the people there were apprehensive about their security.
"The explosion was loud and could be heard far off. The people of the area were already living in apprehension, and this blast now has created further panic. They have also said the police have not taken measures to instil confidence among the villagers," former state women's commission member Bharati Mutsuddi said.
Mutsuddi along with other rights members talked to the villagers and demanded jobs for each of the victims' families along with monetary compensation.
Chief Minister Mamata Banerjee has announced a compensation of Rs. 2 lakh each for the families of nine of the victims and Rs.50,000 for the four who were injured in the blast.
In the wake of the fresh explosion, the Bharatiya Janata Party and the Communist Party of India-Marxist have slammed Chief Minister Mamata Banerjee.
"Eight day after the first blast we now have another explosion. The chief minister has been claiming it to be a mere cracker factory accident. Will she take pains to explain why this explosion took place despite the presence of police?" said state BJP president Rahul Sinha.Sinha, who has been demanding a probe by the National Investigation Agency (NIA) into the matter, sought a statement from Banerjee over the fresh explosion.
"The chief minister needs to explain how come another blast today (Thursday) occurred after eight days of the incident. How long will she continue to try to cover up things? The entire site is cordoned off by the police. Then how come another blast occurred? This is a glaring example of incompetency of the police," CPI-M leader Sujon Chakraborty said.
While a public interest litigation has also been filed before the Calcutta High Court seeking a probe by the NIA, Congress MP Pradip Bhattacharya has written to union Home Minister Rajnath Singh seeking a probe by the premier investigation agency.