A bus crashed and burst into flames killing at least 25 people in India’s western state of Maharashtra in the early hours of Saturday, police and officials said.

“The bus was travelling from Nagpur to Pune when at around 1:35am it met with an accident on Samruddhi Mahamarg expressway, after which the diesel tank of the bus caught fire,” local police told Reuters TV partner ANI.

“The majority of deaths were caused due to burning.”

There were about 30-35 people in the bus, senior police officer Baburao Mahamuni told AFP.

The Indian Express quoted a police official as saying that the bus was of a sleeper type — adapted so passengers could sleep in — and due to the mattresses on board, the bus caught fire instantly.

The report also said officials suspect the driver, who is among the survivors, could have fallen asleep at the wheel. The police were in the process of filing an FIR against the driver.

“The bus was travelling at a high speed when it hit the pole and then a wall on the highway. Due to its impact, the two (front) tyres came off and the diesel tank of the bus exploded, following which the bus caught fire,” Indian Express quoted a police official in its report.

“The driver of the bus has survived. Another driver, who was sleeping inside the bus, has died,” the official added.

Twenty-five people were killed and eight were injured, Maharashtra’s deputy chief minister Devendra Fadnavis said in a post on Twitter.

The state’s Chief Minister Eknath Shinde was quoted as saying by NDTV that the bodies were charred beyond recognition and DNA testing could be employed to identify the victims.

He also said a smart system was being installed on the Samruddhi Expressway to prevent accidents. “The system will check the speed of vehicles and alert them. But it will take some time. Till then, we will have to create awareness among drivers at the toll booths on what precautions need to be taken to prevent accidents at night,” he was quoted as saying.

Shinde and Prime Minister Narendra Modi posted separate tweets expressing sorrow, and said they would pay support to each victim’s family, amounting to 700,000 Indian rupees ($8,500).