The cause of the explosion is not known but the police described it as a “high-intensity” blast.
“Initially, we thought it was a gas cylinder blast. But it is not so. Forensic experts, along with the CID bomb disposal squad, are examining the area,” a senior police officer was quoted as telling the Press Trust of India.
The building also has the office of South Dum Dum Municipality Chairman Panchu Roy, who claimed that he was the actual target of the blast.
Mr Roy stopped short of naming any political party as he said: “Forces currently attacking the ruling Trinamool Congress all over Bengal are behind the attack.”
He called it a planned attack. “They had planned to kill me and other TMC workers, as it would create panic and help them gain foothold in the area,” he told PTI.