Police have pressed four charges against the driver of the bus that burst into flames, killing a least 20 students and three teachers in Pathum Thani on Tuesday.
The driver, Samarn Chankut, 48, fled the scene of Tuesday's tragedy.
He turned himself in to police in Ang Thong’s Wiset Chai Chan district on Tuesday night and was returned to Pathum Thani’s Khu Khut police station for further questioning.
Pol Maj Gen Chayanont Meesati, deputy chief of Provincial Police Region 1, said Mr Samarn told police he was in deep shock when he left the scene of the inferno and fled to a relative’s house in Ang Thong.
His bus was the second in a three-bus convoy taking students from Uthai Thani to an exhibition at the Electricity Generating Authority of Thailand in Bang Kruai district in Nonthaburi.
It crashed and burst into flames on inbound Vibhavadi Rangsit road, near the Zeer Rangsit shopping centre in Lam Luk Ka district, around noon.
Mr Samarn told police questioners they were travelling at 70-80 kilometres per hour when he felt the bus suddenly lose balance, like falling into a pothole.
The bus developed a problem similar to a tyre bursting, or an air bag bursting, the driver said. He lost control of the vehicle, which crashed into a Mercedes Benz before hitting the median barrier. Flames then began spreading rapidly through the bus.
Pol Maj Gen Chayanont said police initially pressed four counts against Mr Samarn - reckless driving causing danger to people or property, reckless driving causing death, careless driving causing physical or mental harm to other people, and failing to provide assistance after an accident. (continues below)
Forensic investigators collect samples from the scene of the bus tragedy in Pathum Thani. (Photo: Pongpat Wongyala)
Investigators were awaiting forensic results and a report on the condition of the bus, including the gas tank conversion, before deciding what charges to bring against the operator of the bus, Pol Maj Gen Chayanont said.
The bus was carrying 38 students, from Kindergarten 2 to Mathayom 3, and six teachers from Wat Khao Praya Sangkharam school in Lan Sak district of Uthai Thani province.
Twenty students and three teachers on the field trip were confirmed killed by the inferno. The survivors were all rushed to hospitals.
Three injured students were in critical condition. Two, aged 7 and 9 years, and were transferred to Thammasat University Hospital. The third, aged 14, was still being treated at patRangsit Hospital for serious burns.
On Tuesday, relatives of 15 of the dead victims provided DNA samples to assist in identifying the dead children. Relatives of the eight other victims were on their way from Uthai Thani province, police said.
Pol Lt Gen Trairong Phiewphan, commander of the Office of Police Forensic Science, said on Wednesday 17 bodies had been identified and the cause of death verified in 11 cases. Identification of the other six bodies should be completed on Wednesday afternoon.
He said the bus had been converted from diesel fuelled to natural gas (NGV). Ten compressed natural gas tanks had been installed. Forensic police would ask the Department of Transport how many NGV tanks were allowed to be installed on the bus.
Acting national police chief Pol Gen Kitrat Phanphet said only six cylinders were listed on the vehicle's registration.
Television news reported the bus was first registered 54 years ago, on Feb 19, 1970, with an Isuzu diesel engine. It had been replaced with a Mercedez-Benz engine and converted to natural gas. It was initially registered as a passenger bus operating on non regular routes with vehicle number 2105472 and engine number 422915-590053. The bus belongs to Chinnaboot Tour, based in Sing Buri.
Pol Lt Gen Kornchai Klayklueng, assistant national police chief, said the bodies of the victims would be taken to Wat Khao Phraya Sangkharam in Uthai Thai province for funeral rites. His Majesty the King had granted all 23 deceased victims royal patronage, he said.