Suspected pro-LTTE activists blasted the railway tracks at Perani station in Tamil Nadu's Villupuram district early on Saturday, minutes before a passenger train was to enter the station.
Luckily for passengers of the Tiruchirapalli-Chennai Rockfort Express, railway authorities warned the train driver in time, and he applied emergency breaks, thus averting a tragedy.
Pamphlets condemning Sri Lankan president Mahinda Rajapaksa's visit to India were found at the blast site, 70 km from Chennai, the police said.
The blast, which was triggered around 2 am on Saturday, ripped the tracks, forming a three-feet wide crater, the police and railway officials said.
"As of now there are no breakthroughs, but we are questioning a few people," DIG (Villupuram range) E. Masanamuthu told HT. "Pamphlets discovered on the site lead us to believe that pro-LTTE groups could be behind this."
Security and patrolling at tracks had been stepped up, he added.
Anti-Rajapaksa protests had erupted in Tamil Nadu last week, with activists slamming him for his government's military campaign against the LTTE last year and the alleged human rights abuses against the island country's minority Tamil population.
For train passengers in the state, the day began with inordinate delays as many trains from south Tamil Nadu to the state capital Chennai were either halted or diverted.
Train services were delayed by more than four hours on Saturday morning, but restored by 9 pm, the authorities said.