The jailbreak unfolded after a medical emergency was staged by inmate Muthu Elangovan, who pretended a seizure to divert guards.
According to Inspector General of Police Vijayendra Bidari, the plot crystallised around 7 pm when a group of inmates voiced anger over denied bail pleas.
The sub‑jail housed 32 undertrials; 17 broke out, while 15 remained confined, some of whom may have played passive roles in the escape.
Guard S. Ramesh, 45, sustained a fractured wrist after being struck by a kitchen knife, and eight staff members were later suspended for dereliction of duty.
Prison Department chief A. S. Venkatesh said the audit will finish by the end of the month, and a full report will be released next week.
Families of the escapees, many of whom had been awaiting bail, reacted with disbelief; M. Srinivasan, mother of one inmate, said the incident shook their faith in the system.