Sabotage can not be ruled out as the cause of a fatal bus blaze that killed 25 people and injured 76 others Friday in southwest China's Chengdu City, said an official on Saturday.

Hu Qinghan, director of the Chengdu Communications Commission, said that according to an initial investigation, self-combustion or a mechanical glitch cannot be concluded as the cause of the blaze.

"The blaze was not fueled by diesel in the oil tank. Investigators found the tank still contained 107 liters of diesel and no mechanical glitch was found in the engine," said Hu.

He said that the bus driver failed to open the cab door after the accident. He used the fire extinguisher on the bus to break the door window, and helped passengers to get out.

The accident occurred in morning rush hour on Friday, when the No.9 bus, with license plate Chuan A 49567, was on its way from Tianhui Township to downtown Chengdu, and caught fire under the Chuanshan Viaduct.

Mao Zhixiong, a government spokesman, said on Saturday that the DNA of the 25 people killed in the blaze has been collected to help confirm their identities, and 20 of the 76 injured passengers on the bus are still in serious condition, most with burn injuries.

Three slightly injured people have been discharged from hospital, he said.

Among the injured, 35 are male and 38 are female. The oldest one is 72 years old, and the youngest is five.

"The bus had air conditioning and only the windows at the rearmost seats could be opened by hand," said 29-year-old Deng Huaqiong. She sat on the second row from the rear and jumped out after someone opened the back window. She suffered slight burns and was receiving treatment in hospital.

Passers-by smashed the windows from the outside, which helped save some of the passengers.

The bus was built in February 2005. It had 270,000 km on the clock.

(Xinhua News Agency June 6, 2009)