The accident occurred at Chitheri area near Arakonam, around 60 km from Chennai, at about 6 a.m. Wednesday, said a southern railway official.
Railway ministry officials in New Delhi and officials in Chennai said one person was killed and 21 others injured in the incident. The rescue work was over, they said.
However, conflicting reports were emerging from Chennai regarding the toll.
Seven express trains were cancelled in Tamil Nadu on that route because of the derailment.
Earlier railway officials in Chennai had said two people were killed in the accident.
--Indo-Asian News Service
