The National Investigation Agency (NIA) must probe the Oct 2 bomb explosion near Budwarn town in West Bengal which killed two people, the CPI-M said Monday.
The blast in Khagragarh "is a very serious issue. There are sufficient grounds to believe that extremist elements are involved," the Communist Party of India-Marxist said.
"The concerned house is owned by a Trinamool Congress worker and it is alleged that a TMC office used to function from the garage in the house," a party statement said.
"The way in which the Burdwan superintendent of police and other police officials have dealt with the incident has raised doubts and questions," the CPI-M said.
"It is essential, therefore, that the investigation into the incident be handed over to the NIA as this concerns the country's security.
"No effort should be spared to uncover the forces behind the bomb-making centre."