Police investigating a fatal bus crash say a fire broke out immediately after the bus overturned on an expressway in Nagoya City, central Japan.

The bus was heading for Nagoya Airport from the city center on Monday morning. The vehicle hit a divider between two lanes on the expressway and overturned before it caught fire.

Two people died. One of them appears to be the bus driver. Six passengers and the driver of a passenger vehicle that collided with the bus were injured.

Police have analyzed video footage captured by the dashboard camera of the car that was driving behind the bus.

Police said on Thursday they have found a fire had broken out from the front part of the bus immediately after it overturned, and the fire had spread all over the vehicle within a few minutes.

Police suspect a fuel tank believed to be installed in the front may have sustained damage when the bus crashed and a spark may have ignited oil that leaked from the tank.