Four police personnel and a staff of Pallabi Police Station were injured after a 'weight machine' that they seized during a drive exploded inside the police station this morning, police said. The injured are: Inspector (Operations) Imranul Islam (48), Sub-Inspectors Sajib Khan (30), Angkush Kumar (28) and Rumi Tabres Haider (28) and a police station staffer Mohammad Riaj (28).