Kolkata, May 7 (IANS): At least 11 people were killed and seven injured in an explosion at a firecracker factory in West Bengal, police said on Thursday. But the BJP has demanded the incident should be probed by the National Investigation Agency (NIA).

The explosion took place late Wednesday at Pingla in West Midnapore district, some 120 km from here.

"Eleven people have been killed and seven others injured in the explosion that took place in a fire cracker factory. The condition of the injured is critical, the toll may rise," Superintendent of Police Bharati Ghosh told IANS.

Ranjan Maity, the owner of the building that housed the factory, has been arrested.

"We have arrested Maity. We have received complaints that the factory was illegal and it was used for manufacturing bombs. We are looking into all aspects," said Santosh Mondal, the sub-divisional police officer of Kharagpur.

Blaming the Mamata Banerjee-led Trinamool Congress government for rise in terrorist activities in the state, the Bharatiya Janata Party (BJP) demanded a probe by the NIA.

State BJP president Rahul Sinha said a probe by the NIA was essential.

"We have seen how the state government tried to suppress facts in last year's Burdwan blast case. We all know the police will never do anything to solve the case so we demand a NIA probe into the incident, Sinha said.

A BJP delegation led by legislator Samik Bhattacharya is slated to visit the area.

"Maity, who has been arrested, is a powerful Trinamool leader from the area. We have apprehension that there may be attempts to pass this incident as cracker factory explosion, which it is not. So it is imperative that the NIA steps in," said Bhattacharya.

Congress leader Abdul Mannan too blamed the ruling Trinamool for the rising acts of terrorism in the state and demanded a through probe into the incident.

Residents, alleging that the factory was used for making bombs, claimed the toll was much higher.

"The explosion was so loud that it shook nearby houses and cracks have also developed. Maity is a criminal and he used the factory to make bombs," a resident said.

"Bodies are still strewn inside the factory. Many more have died. More than 30 people used to work here and most of them aremissing," he said

Some residents also alleged police inaction.

"We have been complaining to the police about the illegal factory and urging action. But they never paid heed. If the police had taken action, so many people would not have been killed," said another resident.