The incident took place at Barrah village under Kankartala police station area. It is yet to be ascertained if anyone has been injured in the explosion, police said.
The party office was locked from outside when the explosion occurred which damaged a big portion of the office, they said.
"The local people claimed that the office was locked at the time of explosion," Kunal Agarwal, Superintendent of Police, Birbhum, said,
"To ensure the nature of explosion some more time is required. So far, no person has been arrested in this connection," he added.
Anubrata Mondal, the district TMC president, alleged that BJP-backed miscreants from Jharkhand attacked the party office with bombs.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)