The engine and three coaches of Erode bound Yercaud Express derailed at Arakkonam near here, Southern Railway officials said today.
Nobody was injured in the late last night's incident, they said.
Some services had been immediately diverted.
Yercaud Express later left for its onward journey today morning following restoration work and was running late nearly by five hours, officials added.
However, the mishap resulted in the delay of about 18 trains arriving Chennai.
The delays ranged between 30-120 minutes, they said.
Track restoration work was on and it was expected to be completed by this afternoon, Southern Railway officials said.