KUALA LUMPUR (Reuters) - Malaysia has identified all 23 people who died in a horrific fire at an Islamic boarding school, an official said on Friday, as calls mounted for tougher regulation after the worst such tragedy in two decades.

People carry a casket containing the body of a victim of the Darul Quran Ittifaqiyah religious school fire during a burial in Kuala Lumpur, Malaysia September 15, 2017. REUTERS/Lai Seng Sin

The fire killed 21 teenage boys and two teachers after it broke out early on Thursday at a “tahfiz” school, where students learned to memorize the Koran.

“We hope and pray this will be the last such incident and preventive actions must be in place and be the order of the day,” said Noor Hisham Abdullah, Malaysia’s director general of health, adding that DNA tests were used to identify the bodies.

There have been 31 similar fire incidents in the past, Malaysian officials said, but media put the figure higher. Among 1,034 fires in religious schools during the two years to August 2017, 211 schools burned to the ground, the Star daily said, quoting fire department figures.

Family members of Mohamad Haikal Abdullah, a 12-year-old who died in the blaze, were furious over reports that the only door to the school’s dormitory had caught fire while metal bars on the windows trapped the boys, leaving them unable to escape.

“From what we understand, there was only one way out, but they couldn’t get through because it was on fire,” said his brother, Faizal Abdullah, as he waited outside a hospital morgue for his sibling’s remains to be identified.

“How could they have escaped? How could something like this have happened? We want to know.”

Fire officials said they found no damage to the electrical wiring of the dormitory, ruling out their earlier suggestion that a short circuit probably caused the blaze.

The incident is being investigated as negligence, the fire chief, Wan Mohd Nor Ibrahim, told state news agency Bernama.

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The school denied a statement by authorities that it had made structural changes without approval from fire officials.

Muslim-majority Malaysia offers a secular education system, but growing conservatism has led to a boom in the number of Islamic religious schools, most privately-run and not overseen by education authorities.

Some offer a curriculum similar to secular schools, but with a greater emphasis on Islamic knowledge, while others provide more specialized education.

Inadequate regulation and training has led to a slew of safety issues at such schools, including reports of fires, abuse, and student deaths, religious leader Mohamad Asri Zainul Abidin said on social media site Facebook.

Some owners had set up schools simply as money-making enterprises or to satisfy their own interests, said Mohamad Asri, the mufti of the northern state of Perlis.

“Some low quality schools, in order to save costs, also take in anyone ready to teach, even when they have nothing to do with the subjects they’re teaching,” he added.

Some religious schools were reluctant to follow government regulations for fear of interference in their administration, said Deputy Prime Minister Ahmad Zahid Hamidi.

Former prime minister Mahathir Mohamad, whose tenure lasted 22 years, said no lessons had been learned in nearly three decades, citing a 1989 tragedy that killed 27 girls at a religious school.

“I’m sad that this kind of incident happened again,” news portal the Malaysian Insight quoted him as saying after visiting victims’ families.

“Safety measures are very important. I hope after this, all schools will review (safety measures).”