Chennai police commissioner Mr A K Viswanathan visited the spot. He told NDTV that "It was hurled on the pathway. We are investigating based on CCTV images. The motive isn't clear yet".
"The fire was immediately put out and none suffered injuries," he said.
Mr Viswanathan, who visited the spot along with senior officials, said a probe was on into the incident and that they were looking into different angles as part of the investigation.
Recently petrol bombs were thrown at the CPI(M) office in Coimbatore. Nobody was hurt in the incident and a car parked nearby suffered minor damages.
With Inputs From PTI