The cause of a bus fire in Shanghai which killed three people and injured 12 others was flammable material being carried on the bus by a passenger, police said Monday.

The case is being investigated further, the police said.

The fire broke out at 9 a.m. when the bus was in Huangxing Road in Yangpu District, in northeast Shanghai.

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

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

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

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

(Xinhua News Agency May 6, 2008)