A passenger bus burst into flames in downtown Beijing early Monday morning, most likely caused by a gas leak, according to officials. No one was injured and authorities have ruled out arson.

The charred ruins of a No. 17 bus that caught fire Monday on Chongwenmenwai Street near the South Second Ring Road in Beijing. No casualties were reported and the cause of the fire is still being investigated.

But the incident, which local residents said was "alarming", took place on a busy Monday morning and less than two weeks from the National Day celebrations on Oct 1. It also increased the latest security tensions in the Chinese capital, after two stabbing cases in central Beijing last week that resulted in two deaths and more than a dozen injuries.

The passenger bus on route No. 17 caught fire just after 6 am yesterday south of the Yutingqiao Bridge near the South Second Ring Road in Chongwen District. The fire lasted for more than one hour.

The two-carriage bus was burned to a blackened skeleton with all the windows destroyed in the heat.

Even though the traffic returned to normal two hours after the fire, residents nearby recalled the scene with shock.

"We heard a rumbling outside the windows," said an employee surnamed Zhao who was on shift in a nearby fast food chain store. "The scene was scary because the big bus seemed to be burning from all places."

"It is fortunate that the bus was empty except for one driver and one conductor when it broke into flames," a spokeswoman surnamed Li at the Beijing Bus Group told China Daily.

The authorities also said the bus was on its way back to the bus terminal when it caught fire, so no passengers were on board. A fire squadron sent three fire engines and more than 20 firefighters to handle the fire.

The accident set off an alarm regarding heavily used buses around Beijing.

"This batch of buses was put into operation nearly 10 years ago. Given their heavy work loads operating in Beijing each day, many of them should be in pretty fragile condition," said Professor Ge Yunshan, an expert on bus engine design with the Beijing Institute of Technology.

Beijing Bus Group officials said Monday they have kicked off an inspection of all natural-gas powered buses.

The city, with more than 20,000 buses in operation, has a fleet of more than 4,100 buses burning natural gas. Crowded locations were tightly watched by more armed police yesterday. Equipped with guns, police officers and armed police watched over each crossing.

Locals and travelers said they had heard of recent incidents in Beijing, but were convinced that security measures will keep the city relatively safe before and during the National Day.

On Saturday, Beijing temporarily banned knife sales in all supermarkets as part of the latest security measures. The move comes after two stabbing incidents in the city.

Flights out of Beijing will also be delayed on the morning of Oct 1 as part of ramped-up security. Authorities implemented a similar airport shutdown last year for the opening of the Beijing Olympics.

(China Daily September 22, 2009)