The crack was noticed by a railway keyman on a routine patrol of the track in Ferok-Kallayi section at around 8.10 AM shortly before the Chennai-Mangalapuram Express was to pass through the area, a railway official said.
The train which by then left Ferok station, about 12 km from here, was immediately stopped.
The track was repaired at about 8.55 AM and the train was allowed to continue its journey at a reduced speed of 10 kmph in the section.
The Kochuveli-Lokmanya Tilak Express, which was following it, also got delayed by 10 minutes, the official said.