A huge boulder and loose soil fell on the track at a spot, displacing the train's rack and pinion system and blocking its movement, they said.
The train had started from Mettupalayam around 7.15 AM.
A few workers brought in from Coonoor, about 11 km from the spot, removed the boulder and soil and repaired the system after a nearly two-hour attempt, they said.
The train later left Hillgrove and was expected to reach Coonoor around 1.30 PM, a delay of more than three hours, the sources said.