The explosion comes close on the heels of Thursday's twin blasts on the Kaziranga Express train in Chennai that claimed a woman's life and left 14 injured.
The crude bomb went off in a house in a residential colony in this temple town, causing damage to the room atop the building in which five persons were injured including an employee of a well-known University.
The trio undergoing treament at the government hospital tricked the police and escaped under the guise of answering nature's call and one of their associates did likewise from the private hospital, police said.
The police have launched a hunt for the injured and are keeping a watch on the lone person who remained in hospital and is suspected to have brought the bomb to the room where it exploded.
The injured Mohan Ram is an history-sheeter hailing from Dindigul, police said.
According to Cuddalore Collector Kirlosh Kumar, who visited the spot, a country-made pistol and material suspected to be used in making explosives were recovered from the house where Arul was staying.
Police said they have launched a probe into the matter from various angles in the wake of the four making good their escape.
On Thursday, when twin blasts had rocked the train in Chennai, an alleged Indian Mujahideen operative from Rajasthan was arrested by police of that state at Parangipettai in this district.
