LAN SAK, Thailand (AP) — The bodies of almost two dozen young students and teachers who died in a bus fire in a suburb of Bangkok were returned late Wednesday to central Thailand, where they began their ill-fated school field trip.

Friends, relatives and Buddhist monks waited past midnight for the last of several convoys carrying remains, as well as relatives who had to travel to Bangkok to help with DNA identification of the severely burned victims.

The bodies were received at Wat Khao Phraya Sangkharam, the temple in this town in Uthai Thani province that houses the school attended by the victims. It is common in much of rural Thailand for Buddhist temples, which serve as community centers, to host schools.

A line of coffins with portraits of the deceased sat in a big assembly hall of the school where grief-stricken relatives huddled. Some went over to touch the portraits of many small children, or stood still in silence in front of them. Funeral services were to begin Thursday morning.

AP AUDIO: Bodies of the children and teachers who died in a Thai school bus fire returned home for funeral

AP correspondent Charles de Ledesma reports police in Bangkok have confirm ed that all the bodies from a fatal school bus fire have been identified.

The tragedy has caused sadness as well as anger. On social media, parents have expressed nervousness about sending their children on school field trips, but more common was outrage about the apparent lack of safety measures. Thailand has long been infamous for having one of the highest rates of traffic fatalities in the world.

Thai police on Wednesday said they were investigating whether the fire was caused by negligence, and filed several initial charges against the driver.

The blaze on the bus carrying six teachers and 39 elementary and junior high school students on Tuesday spread so quickly that 23 were killed while only 22 were able to escape

Three students remained hospitalized, two in serious condition. A 7-year-old girl suffered burns on her face, and a surgeon said doctors were trying to save her eyesight.

The driver, Saman Chanput, was arrested several hours after the accident and charged with reckless driving causing deaths and injuries, failing to stop to help others and failing to report the accident, police said. He had fled the scene, but after being arrested told police he had run to try to get a fire extinguisher from another vehicle, but panicked and ran away when the fire went out of control before he could get any help.

Authorities were investigating if the fire might be caused by negligence by the bus company as well as the driver, and will press charges against all parties responsible, acting police chief Kitrat Phanphet said at a press conference.

While an initial investigation suggested that the driver was not speeding, police found 11 natural gas canisters inside the bus that had a permit to install only six, Kitrat said. Many Thai vehicles use NGV — also called CNG, compressed natural gas — for fuel.

Police have not officially concluded what was the cause of the fire, but have said the driver told investigators he was driving normally until a front tire malfunctioned and set the bus off balance, at which point it hit a car and then scraped against a concrete highway barrier. The sparks from the friction might have set off the highly flammable gas canisters, and ignited the blaze, police said.

Kitrat said the fact that the driver did not immediately stop after feeling he was losing control of the bus could be grounds for negligence.

An inspection of the bus found that its emergency exit could be opened, but it wasn’t clear if it worked properly, said chief of police forensics Trairong Phiwpan. He also said they did not find any emergency window breakers.

In an interview with public broadcaster ThaiPBS, bus company owner Songwit Chinnaboot said the vehicle was inspected for safety twice a year as required and that the gas cylinders had passed safety standards.

Thailand’s Department of Land Transport said it was implementing urgent inspections of all natural gas-fueled buses. The department also will upgrade its safety guidelines to require crisis management training for drivers and safety inspection every time such vehicles are to be commissioned by schools, said Seksom Akraphand, the agency’s deputy director-general.