Five labourers were injured in a cocktail explosion at Banpara in the town yesterday afternoon. Police said some day labourers found the crude bomb while digging earth to fill a low land in Banpara area. The cocktail suddenly went off while being handled by the labourers, leaving five of them injured.  The injured have identified as Saidur, 35, Abdur Rahim, 55, Helal Uddin, 45, Hoji, 36, of Satpakia in Sherpur district and Rafiqul, 27, of Banpara in the town. They were admitted to Jamalpur General Hospital. Later, seriously injured Saidur and Abdur Rahim were shifted to Mymenshingha Medical College hospital.