Unidentified persons hurled a petrol bomb at the house of a businessman at Puduramanathapuram road here early today, police said. A car parked inside was partially damaged, they said. The businessman, Balan, who was sleeping his house woke up on hearing a loud noise, and found his car burning, police said. Though he managed to douse the fire, the car was partially burnt. Witnesses said a group of three persons were involved in the attack. On a complaint, police detained two persons and interrogated them. However, the reason for the attack was not known immediately, police said.