Three people died and 12 were injured when a bus caught fire in Shanghai at about 9:00 a.m. on Monday, said police.

The cause of the fire was still under investigation. The injured have been sent to hospital, according to the police.

The fire was put out within half an hour. Fire fighters estimated there were about 50 passengers on board the route 842 bus.

The fire broke out when the bus was running along the Huangxing Road in Yangpu District, in the northeast of Shanghai.

Normal traffic around the accident site resumed at around 10:30 a.m., as police had moved away the wreckage.

A witness said that passengers on the air-conditioned vehicle failed to open the windows and escape. The only way to get out the bus was through the door.

An elderly woman passenger said she saw the fire break out at the rear of the bus.

"It was chaos. I was holding my granddaughter, when people pushed me off the bus," she said.