More than 20 people died after a bus carrying students and faculty members on a school trip in Thailand crashed and caught fire near the country’s capital, Bangkok, on Tuesday, officials said.

Thailand’s Interior Minister Anutin Charnvirakul said approximately 25 people are feared dead — though authorities have yet to confirm the official rate of death and injuries. Most of the victims are believed to be school-aged children.

Sixteen students and three teachers have been sent to hospital for treatment, Reuters reported.

Though the exact cause of the bus fire is still unknown, Thailand’s Transport Minister Suriyahe Juangroongruangkit said the vehicle was powered by “extremely risky” compressed natural gas.

Suriyahe told reporters at the scene of the double-decker bus crash that Thailand must implement measures to ban vehicles using this type of natural gas as fuel.

Dozens of resucers and firefighters surround the burned shell of a double-decker bus.

Rescue workers and firefighters surround a burned-out bus that was carrying students and teachers on the outskirts of Bangkok on Tuesday.

MANAN VATSYAYANA/AFP via Getty Images

Video and images from the devastating bus crash show rescuers surrounding the scorched vehicle as it lay under an overpass. The inferno was reported around noon local time and lasted less than an hour before it was stifled.

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Once the large plumes of black smoke had mostly ceased and the burned-out vehicle was deemed safe to enter, rescuers were seen carrying the wrapped bodies of victims out of the wreckage.

The bus was transporting 45 passengers at the time of the crash — six teachers and 39 elementary and junior high school students, the Associated Press reported. There have been discrepancies among local media reports about how many people were onboard the bus at the time of the incident.

The bus was travelling from the central Uthai Thani province when it caught fire in Pathum Thani province, north of Bangkok.

A woman covers the eyes of a young girl as they walk alongside family members in the evening light. They are all crying.

A relative of a student who died in a bus fire covers the eyes of a child who was travelling on a separate bus as part of the same school trip as they walk past the burned wreckage near Bangkok on Tuesday.

MANAN VATSYAYANA/AFP via Getty Images

The incident remains under investigation.

According to the BBC, some witnesses said a front tire on the bus burst and the vehicle crashed into a concrete highway barrier.

The inferno began quickly after the crash. Many of the buses’ occupants were unable to escape, witnesses recalled.

At a press conference Tuesday, acting police chief Kittirat Phanphet said the fire was likely caused by a spark from the exploded tire that lit the gas cylinder used to power the vehicle.

The bus driver reportedly fled the scene of the crash, though Thai officials said they are searching for him.

Some of the deceased have yet to be identified because of the severity of the burns to their bodies.

Rescuers and firefighters stand behind caution tape, beside a burned shell of a double-decker bus.

Firefighters and rescue workers stand next to a burned-out bus that was carrying students and teachers on the outskirts of Bangkok, on Tuesday.

MANAN VATSYAYANA/AFP via Getty Images

Thailand’s Prime Minister Paetongtarn Shinawatra expressed her sympathy for the victims on X.

“As a mother, I would like to express my deepest condolences to the families of the injured and deceased,” she wrote in Thai.

Shinawatra said the Thai government would cover the surviving victims’ medical expenses and would provide financial compensation to the families of those who died.

There were no other vehicles involved in the bus crash.

News of the accident prompted criticisms over the safety of children travelling long hours across provinces on roads notorious for high rates of traffic accidents and deaths.

The World Health Organization estimates that every year, 20,000 people are killed and a million are injured in road accidents in Thailand. The country has one of the worst road safety records in the world.

With files from The Associated Press