At least 15 bus passengers were burnt to death and over 28 critically injured in a fire triggered by a suspected gas cylinder blast in the vehicle at Kailaras, 45 km from Morena on Monday evening, official sources said.

The fire spread rapidly and within seconds engulfed the entire bus, on way to Sabalgarh from Morena, when it was passing by Kailaras police station, making it virtually impossible for the passengers to escape, they said.

Those rescued sustained 80-90 per cent burns, and were sent to hospitals in Morena, Kailaras and Gwalior, Morena District Collector Amit Rathore said.

A probe will be conducted to ascertain as to how a gas cylinder was being transported in the vehicle, Chambal Commissioner J T Ekka said.

Chief Minister Shivraj Singh Chouhan has announced financial assistance of Rs 50,000 each to the families of the deceased, Rs 15,000 for critically injured and Rs 5000 each for those with minor injuries.