Four persons were injured in a bomb explosion in an under construction house at Rajat Boalia under Bishnupur police station in South 24 Parganas district, the police said.
The blast took place in the second floor of the three-storey house and the spot was throughly washed before the policemen reached there, the police said.
The injured, who were hospitalised, said the blast occurred while they were making bombs but the police were not convinced.
The type of injury sustained by the four did not match with the one usually seen in such cases, the police said.
