Five train cars derailed in Tuesday's accident, about 50 miles (80 kilometers) southwest of Chennai, the capital of Tamil Nadu state, said Shalendra Babu, a senior police official.
By early Wednesday, the death toll stood at 10, police official K.M. Babu told The Associated Press. Another 52 people were injured, he added.
S. Nagarajan, the district administrator, said rains initially hampered rescue efforts but all the injured had been moved to hospitals.
Press Trust of India reported that several trains were canceled or delayed because of the accident.
The accident's cause was being investigated, said Railways Minister Dinesh Trivedi.
India's railroad network is one of the largest in the world and carries about 14 million passengers each day. Accidents are common, with most blamed on poor maintenance and human error.
