A low-intensity explosion took place in Hatia-Bhubaneswar Garib Rath Express near Rourkela in Orissa -- one of the five states where Maoists called a 48-hour bandh from Monday.
There have been no casualties in the blast, said the local railway police.
The blast took place in the toilet of G-9 coach of the train late on Monday night near a Maoist-dominated area, they said, adding that the incident came to light only after the train arrived Bhubaneswar on Tuesday morning.
Senior police officers and forensic experts were examining the coach in a bid to ascertain the nature of device or material that triggered the explosion. Efforts were on to ascertain whether explosive device had been planted inside the train or if a bomb had been hurled from outside, a senior railway police officer said.
Sniffer dogs have also been brought into service for thorough inspection of the train.