He had given many tips to police on car theft cases and had asked police corporal for help after his arrest on Feb 6.
Officers from the Serious Crime Unit say when they left the Bandar Baru Klang police station, Balamurugan and two other detainees were in good condition.
Investigating officer Inspector Mohd Noor Husri Johari says he was told to rearrest Balamurugan for another robbery case and seek remand the next day.
He says officer punched and kicked Balamurugan in the chest and legs during questioning.
Photos displayed during public hearing into his death show him wearing only purple shorts and lying close to the bars of his cell.
Police officers say they heard shouts of 'help' and 'aduh' coming from the room next door but did not go to check.
The hearing session is open to the public and media, says EAIC chairman Yaacob Md Sam.
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