A gas pipeline explosion near a mosque in Bangladesh has killed 17 people and injured dozens with critical burns as worshippers were about to end their prayers, officials said on Saturday.

The explosion, which fire service officials suspect was caused by leakage from the pipeline, occurred on Friday night at a mosque in Narayanganj district, just outside the capital, Dhaka.

Dozens were rushed to Dhaka’s state-run specialised burn and plastic-surgery hospital, most of them with severe burns.

By Saturday afternoon, 17 people, including a seven-year-old boy, died after they sustained burn injuries, Samanta Lal Sen, coordinator of the burn unit, said.

The death toll could rise further as many of them were in critical condition, Sen said, adding that doctors were treating at least 37 people with burns on up to 90 percent of their bodies..

“I saw smoke was belching out of the mosque after the sudden explosion with a big bang and people were screaming. Some were rolling on the street as they tried to put out the flames on their bodies,” Mohammad Ratan, a local resident, said.

Fire officials said gas that accumulated from a leak in a pipeline running underneath the mosque likely triggered the explosion.

“We primarily suspect that gas leaked from the pipeline and accumulated inside the mosque since the windows were shut. When the air conditioners was turned on, due to sparks the gas could have exploded,” said Abdullah Al Arefin, a senior fire service official.

Local TV stations reported that because of the impact of the blast, at least six air conditioners also exploded inside the mosque.

Authorities have launched an investigation into the blast.

In Bangladesh, safety regulations are often flouted in construction. Hundreds are killed each year in fires in the nation of 168 million people.

Faulty installation of gas lines are often reported by Bangladeshi media, while unplanned road-digging work often leads to disasters in the country which is seeking rapid industrial expansion and economic development.

In February last year, an inferno in Dhaka’s old quarters killed 78 people. One month later, 25 people were killed when a blaze engulfed an office building in the city.