Bangkok Post – Forensic police find 'gas leak' behind fatal bus fire

A forensic police investigation concluded that a gas leak was the cause of the bus fire tragedy that killed 20 students and three teachers on Tuesday.

Police Lt Gen Trairong Phiewphan, commander of the Office of Police Forensic Science (OPFS), said yesterday that an initial investigation revealed the gas leak occurred at the front of the bus.

However, it is not yet clear what caused the sparks that ignited the flames or why the gas leaked, he said.

Experts in vehicle gas systems are invited for further information.

An inspection by OPFS officials and experts also revealed that 11 compressed natural gas (CNG) tanks were installed in the bus.

A House of Representatives transport committee yesterday invited officials from the Department of Land Transport (DLT) and the Automotive Engineering Bureau (AEB) to explain the cause of the fire and discuss possible solutions.

Jirut Wisanjit, the director general of the DLT, told the committee that six of the 11 CNG tanks installed in the bus were registered, but the remaining tanks were not.

The inspection revealed that the gas leak came from one of the unregistered tanks, which had not been checked by engineers, he said, adding that police were working with the department to find out who was responsible.

“How could it happen that the officials did not notice the excessive number of gasoline tanks when inspecting the bus?” asked Mr. Jirut.

AEB director Cheep Nomsian told the House committee that the bus involved in the accident was a single-deck vehicle and not a double-decker and that the emergency rear door was functional.

The inspection revealed no evidence of front tire explosion, as previously reported, he said, adding that the front wheel shaft of the bus was broken and showed signs of scratches on the road surface.

He also said a fuel line that carries gas from the tank to the engine came loose, causing the leak. Initial reports from first responders indicated that the front left tire had burst, causing the wheel to catch fire. The driver then lost control and the bus hit the central barrier. The vehicle was quickly engulfed in flames.

Following the incident, the DLT suspended the transport operating license granted to Panisara Chinnaboot, the operator of Sing Buri-based Chinnaboot Tour, Mr Jirut said.

The license will be revoked if the investigation finds that the company's negligence caused the tragedy.

Mr. Jirut also pointed out that Kanittha Chinnaboot's registration as the company's Transport Safety Manager (TSM) was revoked and an investigation was launched against Alternative Resource Engineering Co., which provides inspection and testing services for gas-powered vehicles.

The driver's license of the bus driver Samarn Chanphut (48), who turned himself in to the police on Tuesday evening, was also revoked. He faces having his driver's license revoked if he is found guilty.

All 13,426 vehicles with CNG will be checked within 60 days.