Anxious moments prevailed at the central jail near Salem on Thursday when an helicam was found flying over the prison, police said.
The wardens noticed the helicam moving over the jail at about 7 AM and immediately informed superintendent Tamilselvan who managed to grab it, the police said.
The jail officials caught four people outside the prison as they had released the helicam, they said.
The four, working for a Chennai-based firm, told the officials that they were measuring the grounds for expansion of roads in the area and the helicam was part of the process.
The jail authorities lodged a complaint with the police and further investigations were on.