Flammable oil-like material carried on board by a passenger triggered Monday's bus fire in Shanghai that left three dead and 12 injuries, police said Tuesday.

The police are not able to specify the nature of the oil, saying further investigation is underway.

Two female victims were Shanghai natives, but the identity of the third man remained unknown, according to police.

The fire broke out at 9 a.m. Monday when the route 842 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 bus.

(Xinhua News Agency May 7, 2008)