Vellore Superintendent of Police I Eswaran told PTI one passenger was killed and 33 injured in the mishap. The injured have been admitted to the Government hospital at Arakkonam.
The derailment occurred at about 0550 hours, a Railway official said.
Top officials of the Southern Railway visited the spot and commenced an initial probe into the cause of the derailment.
Rail traffic on the Arakkonam sector was disrupted. Railways cancelled about seven trains, including those bound for Bangalore, and diverted some others.