The bus, operated by Raj Kalpana Travel Agency, caught fire at about 11.20 p.m. on Wednesday near the 33‑km milestone of the Yamuna Expressway, killing nine of 35 aboard.
Earlier this week, the manager, Vikas, was summoned from Delhi’s Kashmere Gate, questioned, and arrested on Friday; he is now in 14‑day judicial custody.
Police say the driver and conductor had reported a gearbox problem to the manager days before, but the complaints were ignored, leading to the fatal blaze.
Three other men—drivers Pawan and Yogesh Dixit and conductor Rohit from Kanpur Dehat—were arrested in February; they allegedly abandoned the bus after the fire.
The vehicle, registration BR32PA8647, had accrued ₹1.75 lakh in fines across 19 challans, according to RTO officer Rajesh Mohan.
The investigation, conducted in cooperation with the Transport Department, will proceed with further action after the court hearing scheduled for next week.