Another 43 people with serious burns were taken to a hospital in Nashik, a city in Maharashtra state, said police officer Bhagwan Adke, AP reported.
Most passengers were sleeping when the bus caught fire around 5 a.m. and the vehicle was completely burned, the Press Trust of India news agency said.
Some people living near the highway reached the spot but couldn't help as the raging fire engulfed the vehicle. The rescue work started after the fire service and police doused the blaze, Adke said.
Eknath Shinde, the top state elected official, said the cause of the fire is being investigated.
Prime Minister Narendra Modi said he was anguished by the bus tragedy. "May the injured recover at the earliest. The local administration is providing all possible assistance to those affected," Modi tweeted.
Nashik is nearly 200 kilometers (120 miles) northeast of Mumbai, the capital of Maharashtra.
Hundreds of thousands of people are killed or injured annually on India’s roads. Most accidents are blamed on reckless driving, poorly maintained roads and aging vehicles.