He allegedly had more than 20 criminal cases filed against him.
A 30-year-old man died in police custody in Tamil Nadu's Chennai on Sunday evening, the second such incident in the state in two months.
Rajasekar was taken into custody by Kodungaiyur Police on Saturday. He allegedly had more than 20 criminal cases filed against him.
Police said that Rajsekar, a resident of Thiruvallur district, had confessed to the crime and in the process he reported uneasiness.
"We rushed him to a nearby hospital where he felt better after the treatment. We then brought him back to the police station," officials said.
However, he developed complications again and was declared "brought dead" by the Government Stanley Hospital, officials said.
"Five police personnel including an Inspector and a Sub Inspector have been suspended," said T S Anbu, Additional Commissioner of Police, Chennai.
Tamil Nadu Director General of Police, Sylendra Babu, has ordered the Crime Investigation Department (CB-CID) to probe Rajasekar's death.
Leader Opposition Edappadi K Palaniswami slammed the state government over Rajasekar's death and urged the High Court judges to look into the matter.
"In Tamil Nadu, another lockup death has occurred. In the DMK Government lockup death has become continued and there are no actions to stop lockup death. We request High Court Judges to come forward to take lawful actions on lockup death which happened during DMK Government," Mr Palaniswami said.
Earlier, a 25-year-old man, V Vignesh, who was arrested in April this year for alleged possession of drugs and was reported "dead" the next day.
Six cops were arrested on murder charges after a post-mortem investigation found injuries on Vignesh's body.