BANGKOK: Grieving families wept as they offered prayers on Wednesday for 23 children and their teachers killed in a horrifying Thai school bus fire, as the government vowed a crackdown on unsafe vehicles.

Police have arrested the driver of the coach, which erupted into flames after hitting a barrier on a highway in northern Bangkok on Tuesday.

The remains of the 20 children and three teachers were returned to relatives after DNA testing was needed to identify them because they were so badly burned in the inferno.

The bus was one of three carrying children from Wat Khao Phraya Sangkharam school in the northern province of Uthai Thani on a field trip to a science museum in northern Bangkok.

White-and-gold coffins carrying the bodies were loaded onto ambulances at a Bangkok hospital mortuary to make the journey to Uthai Thani, accompanied by their relatives.

Parents sobbed uncontrollably as they offered prayers for their sons and daughters at the site of the tragedy, where the convoy of ambulances stopped before making its way north.

Monks and staff at the school in rural Uthai Thani, around 200 km (120 miles) north of Bangkok, began preparations for five days of funeral prayers for the victims, who are expected to be cremated on Tuesday.

Teachers and students at a number of schools around Thailand laid white flowers to mourn those killed in the blaze, believed to be the kingdom's deadliest road accident in a decade.

Thailand has the second-worst road safety record in Asia, after Nepal, with around 20,000 deaths reported every year – an average of more than 50 a day.

Acting national police chief Kitrat Phanphet told reporters that the driver – who initially fled the scene – was arrested late on Tuesday and faces charges of causing death by careless driving.

But Kitrat also said the initial investigation points towards a problem with the bus itself.

The bus was fuelled by compressed gas and investigators believe the tanks may have ignited, explaining the devastating speed and intensity of the blaze.

Deputy transport minister Surapong Piyachote announced urgent checks on gas-fuelled buses.

"To avoid this kind of tragedy, the department of land transport will recall 13,400 buses using gas and any that do not meet the standard will be seized," he told reporters, saying the process would take about two months.

Speeding, drink driving and poor vehicle standards all contribute to the bloody toll on the kingdom's roads.

Weak enforcement of rules, exacerbated by rampant corruption in the police, has also long undermined efforts to beef up road safety.

Save the Children said the tragedy should be a wake-up call for Thai lawmakers.

"Despite many initiatives launched by the government, Thailand's road death statistics remain at alarming levels," the NGO's Guillaume Rachou said in a statement.

  - AFP