LAN SAK, Thailand (AP) — Mourners wept and monks prayed at a cremation ceremony Tuesday in a small town in central Thailand for 23 young students and teachers who died in last week’s bus fire on a school field trip.

A large cremation site was set up close to the temple in Lan Sak town whose compound hosts the school that was attended by the victims. Several furnaces with tall chimneys were erected, with floral adornments placed in front of them.

Six teachers and 39 elementary and junior high school students were on the bus when it caught fire on Oct. 1 on a highway in Pathum Thani, a northern suburb of Bangkok. It spread so quickly that only 22 people were able to escape.

After forensic work in Bangkok made positive identifications of the badly burnt bodies, the victims’ remains were were returned to their hometown for funeral rites that began last week.

The tragedy sparked national outrage over insufficient safety procedures and pushed the authorities to take immediate legal action. Police arrested the driver of the bus for alleged reckless driving and announced they were charging the woman in whose name the bus was registered with negligence causing death.

Transport officials were being scrutinized after information emerged that the bus had passed an inspection about four months before the fire. In the wake of the accident, investigators found that the bus was fitted with 11 natural gas canisters although it had a permit for only six.

Officials have said that the bus, which was more than 50 years old, had been modified to run on CNG — compressed natural gas — which is often used especially by commercial vehicles to save money. Police They believe that a gas tube from one of the canisters had come loose, with sparks then setting the leaking gas on fire.

The more than 13,000 buses running on CNG were ordered inspected within 60 days, while the Education Ministry suspended school study trips in the meantime.