At least 45 people were killed when a seven-storey building caught fire in Bangladesh, forcing some to leap from windows to survive.

Firefighters said on Friday that glaring safety lapses had caused the fire and gas explosions at the venue in the capital city of Dhaka. 

The blaze started during the night at a popular biryani restaurant at the bottom of a commercial property in the affluent Bailey Road neighbourhood.

The entire building, home to several other eateries, was engulfed by flames that took fire crews two hours to bring under control.

Fire service operations director, Rezaul Karim, told AFP the blaze had been made worse by numerous cooking gas cylinders stored haphazardly in stairwells and restaurant kitchens.

“People heard the explosions of several gas cylinders during the fire,” he said.

Main Uddin, the national fire services chief, said the building lacked safety measures.

“It did not have at least two staircases or fire exit,” he told AFP. 

“Most of the people died from suffocation.”

Fire officials earlier told reporters they suspected the fire began when one of the gas cylinders accidentally caught fire.

Police inspector, Bacchu Mia, told AFP that another person had died on Friday morning while being treated in hospital.

“The death toll is now 45. The conditions of 15-16 injured people are critical,” he said.

Members of the public helped fire crews carry hoses and rescue survivors who clambered down the outside walls to safety.

“We were at the sixth floor when we first saw smoke racing through the staircase. A lot of people rushed upstairs,” Sohel, a restaurant manager who gave only his first name, told AFP.

“We used a water pipe to climb down the building. Some of us were injured as they jumped.”

At one point at least 50 people were on the rooftop waiting to be rescued by fire cranes, Kamruzzaman Majumder, an environmental science professor who was stranded, wrote on Facebook.

Police investigators were seen walking inside the gutted building and documenting the wreckage on Friday morning, hours after the government ordered an investigation into the fire’s origins.

Hundreds of family members rushed to the nearby Dhaka Medical College Hospital overnight as ambulances brought the dead and injured to the clinic.

Explosions and fires are frequent in buildings and factories across Bangladesh, where safety standards are lax and corruption often allows them to be ignored.

Deadly fires are typically caused by gas cylinders, faulty air conditioners and bad electrical wiring.

Bangladesh’s worst fire took place in 2012, when a fire ripped through a garment factory on Dhaka’s outskirts, killing at least 111 people and injuring more than 200 others.