Of the four, three were students aged between 16 and 25 years and the identity of the fourth person was yet to be established, police said, adding that six persons were also injured in the incident.

Tamil Nadu Chief Minister K Palaniswami condoled the deaths and announced a solatium of Rs 1 lakh each to the kin of the deceased and Rs 50,000 each to those grievously injured.

The incident came in the wake of a similar one last night, in which two persons were killed at a distance of about 50 metres from the site of today's accident at the same station.

"Four men died in the incident and six others were injured," Health Secretary J Radhakrishnan told reporters.

One of the injured received treatment as an out-patient at a government hospital, he said.

Medical teams comprising specialists, including vascular surgeons, were formed to treat the injured, who were admitted as in-patients to the Government Royapettah Hospital and the Rajiv Gandhi Government General Hospital, the health secretary added.

Among the injured was a man whose legs were severed, he said.

The commuters were travelling on the footboard due to the peak-hour rush.

Senior officials, including Kanchipuram Collector P Ponniah and those from the railways and police, inspected the scene of the accident.

Health Minister C Vijayabaskar, Fisheries Minister D Jayakumar and senior government officials, including the health secretary, visited the injured at the hospitals and inquired about the treatment modalities.

On allegations from some commuters that the incident took place due to the diversion of the suburban train to the mainline track for fast trains, Chennai Divisional Railway Manager Naveen Gulati said it was done as there was no power supply in the suburban line.

Abutting the track for fast trains is a wall dividing the railway lines.

The victims died after they hit against this wall.

"Usually, the suburban train (40701) from Chennai Beach to Tirumalpur runs on a suburban track. Even in the morning, it was allotted the same track, but was later shifted to the fast suburban line as there was no power supply in an overhead wire on the other track," Gulati told PTI.

It was a usual practice to make such changes, he said.

The Electric Multiple Unit 40701 takes around three hours to complete the 109-km journey between Chennai Beach and Tirumalpur, with around 35 stops en route.

The Southern Railway said the habit of travelling on footboards led to the tragedy, adding that it would take steps to avoid such incidents, though there was no violation on its part.

"It was noticed that there was no infringement as per Railway rules. However, in view of the unfortunate incident, the matter is being studied by the Railway to identify the further steps to be taken to avoid such incidents," a railway release said.

The general manager, Southern Railway has advised to deploy additional RPF and GRP personnel to guide the passengers.

"Passengers are requested to avoid travelling on the footboard and avoid hanging outside the train, risking their own lives and that of the co-passengers," the release added.