Railways sources told IANS that the incident occurred on the Lucknow-Rameswaram Express in the early hours of Saturday morning.

The six victims from Uttar Pradesh were on a pilgrimage tour to Rameswaram, the sources added.

There were a total of 55 passengers in the affected coach, which was attached at Nagercoil on Friday.

The blast of a gas cylinder, which was illegally smuggled inside the coach for cooking purposes, caused the fire, the sources told IANS.

Meanwhile, of the 20 injured persons, four are said to be in serious condition.

The mishap occurred when the train was stationed at a yard, 1 km out of the Madurai railway station and passengers were about to leave for the Meenakshi temple for darshan.

Fire and Rescue services department reached the spot and doused the fire.

Many people had already alighted when the train had reached the Madurai railway station.

Madurai District Collector Sangeetha told media persons that the injured have been shifted to the hospitals and treatment is is underway.

She also said that the cause of the fire will be further probed.