DHAKA: At least 22 people have been killed and 70 injured, many critically, in a huge fire triggered by a boiler explosion at a Bangladeshi packaging factory, officials said Saturday as firefighters struggled to contain the blaze.

Around 100 people were working when flames tore through the four-storey building in the industrial town of Tongi, just north of the capital Dhaka.

Factory inspection department head Syed Ahmed said the death toll had risen to 22 following the boiler room blast at the Tampaco Foils Limited factory, which supplies foreign and domestic brands.

“We still have not controlled the blaze and we fear some workers are still trapped in the factory,” police inspector Aminul Islam told AFP.

Parvez Mia, a doctor at the Tongi government hospital, told AFP at least 70 people were injured.

“Most of them had burn injuries. We sent the critically injured victims to the hospitals in Dhaka,” he said.

“Several of them are very critical,” he added.

Factory electrician Mohammad Rokon, 35, escaped with minor injuries.

“I was working inside the office room when I heard an explosion and felt a tremor. Then suddenly the ceiling started to fall on me,” he told AFP from his hospital observation bed.

“I almost became unconscious. But I forced myself to go out with the help of my mobile phone's flashlight.”

Machine operator Rubel Hossain was two minutes away from entering the factory when the blast occurred.

“I heard a huge explosion and saw smoke and fire coming out of the factory,” he said.

“I am simultaneously feeling lucky and heartbroken,” he said, tears streaming down his face as he helped rush the many injured to hospital, blood staining his T-shirt.

The tragedy struck as families were preparing to celebrate Eidul Azha.

“My brother Delwar Hossain told us last night he would take us to our home district of Sherpur. Now he is going to be buried there,” said Khaleda Begum, the sister of a factory worker killed in the accident.

“Eid is ruined for our family.”

Chemicals may have been stored on the ground floor of the factory, helping to explain how the blaze that began at 6:00 am (local time) spread so fast, said Tahmidul Islam of Bangladesh's industrial police unit.

“What we have heard is that there were chemicals stored on the ground floor. As a result, the fire took no time to spread,” Islam told AFP, adding scores of fire officials were still battling to bring the blaze under control.

According to the company's website, the packaging factory supplies multinational and domestic brands including British-American Tobacco Bangladesh Limited and Nestle Bangladesh Limited.

The head of Bangladesh's factory inspection department said a committee had been set up to investigate the fire.

“They'll probe why the fire occurred and whether the factory lacked proper fire safety measures. They will also suggest how we can improve fire safety of local factories,” Ahmed said.

Fires, accidents common

Fires and other accidents are common in the factories that make up the $27-billion garment industry in Bangladesh, the world's second-biggest apparel exporter after China.

In November 2012, at least 111 workers were killed when a devastating fire engulfed a nine-storey garment factory in the Ashulia industrial area, outside the capital Dhaka.

The accident was followed by an even bigger tragedy six months later when 1,138 people died after another clothing factory complex collapsed, trapping over 3,000 workers.

The Rana Plaza tragedy triggered international outrage and put pressure on European and US clothing brands to improve pay and conditions at the factories that supply them.

Western brands subsequently improved safety standards and inspections for suppliers, dramatically reducing incidents of fire and other accidents at export-orientated factories.

Fires in garment factories have dropped from 250 in 2012 to just 30 in 2015, with no fatalities that year, according to Bangladesh fire department figures.

But thousands of local factories supplying the domestic market have done little to address safety concerns.

Workers are often crammed in elbow to elbow, while fire escape stairwells are routinely blocked or padlocked closed, ostensibly to prevent theft.

Building regulations are rarely enforced and volatile chemicals are often improperly stored, while official safety inspections are few and far between.