Railway authorities are still puzzled about the cause of the fire that had broken out in bogie number 99480 of the Falanuma passenger train at Gulbarga station on October 15.
While they have ruled out sabotage as a likely reason, they are now probing the possibility of the fire being caused by a man and his girl friend who tried to immolate themselves.
Two people had died in the fire and several others were injured.
The probe team suspects that two people had entered the train at Gulbarga station and set themselves ablaze, leading to the mishap.
Preliminary reports, based on accounts of eye witnesses, suggest that an auto rickshaw driver and his girlfriend entered the train at Gulbarga station and set themselves on fire.
The investigators had earlier suspected sabotage as the cause behind the fire after it was reported that some men were spotted with kerosene cans inside the train. But this angle was ruled out after the first round of investigations.
Currently, the investigators are focusing on the suicide of the couple as a likely cause behind the mishap. They are trying to collect more evidence and questioning people known to the couple to find out more information.