A fire on a crowded passenger bus in central Indonesia killed 12 people Saturday, including three children, police said.

The driver pulled over when he saw flames pouring from the engine, said Lt. Col. Nuryadi, a police chief in Central Kalimantan province, adding that the blaze spread quickly through the bus.

Nearly 50 passengers escaped through the back exit, but 12 died, including a baby and two other children, said Nuryadi, who uses only one name. Six other people were hospitalized with burns, he said.

Most of the victims had been sitting in the bus's front seats.

It was not immediately clear what caused the blaze, but it appeared to have been an accident, Nuryadi said. The driver was being held for questioning.

The fire occurred in Palangkaraya, around 540 miles northeast of the capital, Jakarta.

Road accidents are common on Indonesia's crowded highways, where buses and trucks are poorly maintained and traffic laws are often ignored.