The country bomb blast occurred inside a house in Tsunami Colony in Idintakarai near Kudankulam Nuclear Power Plant in the state's Tirunelveli District.
Police have filed a against People's Movement Against Nuclear Energy (PMANE) activists and others as well.
Meanwhile, security has been tightened around the plant.
Site Director R S Sundar confirmed that police are continuing with their probe of the incident.
Media quoted Tirunelveli Superintendent of Police Vijayendra Bidari, as saying that cases have been registered against PMANE activists S P Udayakumar, Pushparayan, Mukilan and several others.
Initial investigations point that crude country bombs were stored in the house illegally and that they went off accidentally.
--ANI (Posted on 27-11-2013)