The bus, registered in Bihar as BR32PA8647, was on a Delhi‑Mahoba run when it caught fire on the Yamuna Expressway on April 20.
Passengers had warned the driver and conductor about a burning smell minutes before flames erupted, but the crew laughed off the complaint and continued smoking inside the vehicle.
A preliminary investigation points to a blast in the bus’s air‑conditioning unit that ignited engine oil, sparking the rapid spread of fire.
Police have detained the driver and conductor for questioning; the bus had accumulated more than 60 traffic fines, including ₹1.7 lakh in unpaid penalties.
Mahoba BJP District Treasurer Neeraj Gupta’s wife, Sunita, and 13‑year‑old son Shashank, both from Rajmandir, Charkhari, perished after the blaze; the family’s home in Rajmandir was visited by former MP Pushpendra Singh Chandel.
Investigators are tracing the exact cause of the fire and will review maintenance records, while a court hearing is set for next month to determine liability.