Paripoorna Kannan, his wife and 12-year old daughter were charred to death in the car, which was gutted, on a side road off the Palayamkottai-Tiruchendur highway, police said.
Passersby saw the car go up in flames with a loud sound and alerted the police who rushed to spot and retrieved the bodies.
Police said they recovered a purported suicide note from the house of the businessman stating that due to some health problem he was unable to continue his business. Besides, he had also mentioned that he had given Rs 1.75 crore as loan to two of his friends and they neither paid interest nor returned the money, police said.