The fire which engulfed Gautami Express in Andhra Pradesh early this month, killing 31 people, was due to some highly inflammable substance kept in a sleeper coach, a railway inquiry committee said on Tuesday.

The commissioner of Railway Safety, in its provisional findings, said the incident had occurred due to some highly inflammable substance kept by unidentified persons in the S-10 coach of Secunderabad-Kakinada Goutami Express.

Five coaches went up in flames in Warangal district of Andhra Pradesh in the wee hours of August 1 in which 31 passengers were killed and nine injured.

The fire broke out in one of the bogies in the moving train at 0115 hours near Kesamudram railway station, about 200 km from Hyderabad, and soon spread to four other bogies.

The tragedy struck when the passengers were fast asleep making it impossible for many of them to escape from the blaze.