During a surprise check, the officials found a mobile phone hidden inside a switch box at the cell where the gangster had been lodged since he was detained under Goondas Act a few months ago. It was a basic model phone and there was no SIM card inside, said a source. Puzhal police registered a case and are inquiring if Radhakrishnan had been using the phone and for how long. Radhakrishnan was arrested by city police in August last year during a vehicle check since he had been absconding for six months after coming out on bail. Later, he was detained under Goondas Act. Radhakrishnan is an accused in 29 cases including murder, kidnap and extortion and has been notorious for operating from the prison itself.