MADURAI: The body of B Ajith Kumar , 27, a security guard who died in police custody in Sivaganga on Saturday after being detained in connection with a theft, bore multiple external injuries, said sources privy to the preliminary postmortem report.Doctors informed police that the injuries — individually or collectively — may not have independently caused death, as they appeared to be “external and superficial.”They have sent samples of vital organs and tissues for further pathological tests, including biopsy, to confirm the cause of death.Chief minister M K Stalin , who chaired a meeting with senior bureaucrats and police officers in Chennai on Monday, warned of stringent action against police personnel accused of lock-up deaths. Five police personnel have been arrested in connection with the custodial death.Meanwhile, Madras high court asked why police treated an unarmed man in custody in such a manner. Earlier, BJP state president Nainar Nagenthran questioned Stalin’s silence on the issue. DMK allies too criticised the state police over the custodial death.