SAVAR: Bangladeshi rescuers pulled dozens more people alive from a razed garment factory building on Friday as the US pressed for a crackdown on deadly negligence of safety norms in the clothing industry.

The overnight rescue of 45 people provided new hope to thousands of anguished relatives at the scene, on Dhaka's outskirts, but the death toll crept up to 273 as emergency workers battled against the stench of decaying bodies.

“The odour is so foul, sometimes you feel like vomiting. It's difficult to work here 20 minutes at a stretch,” said Mohammad Tareq, a garment worker himself who is one of hundreds of volunteers to have joined the rescue effort.

But the hope of retrieving more survivors was driving the rescuers on, nearly 48 hours after the eight-storey Rana Plaza complex pancaked, setting off new anger at reckless garment factory owners and their Western brand customers.

“Please brother, save us! We're around 15-20 people here. Save us. We want to live,” one woman named Nasima, trapped on what used to be the complex's fifth floor, told Tareq.

“We've passed water and fruit juice to them. We hope they will be rescued in the next hours,” Tareq told AFP, as rescue workers toiled through the night with floodlights and hand torches to reach those still alive.

To wild applause from the crowd of relatives gathered at the scene, an army spokesman initially announced late on Thursday that 40 survivors had been discovered together in one room. But that figure was later revised to 24.

“I still haven't found my son,” said a farmer who came up from the southern district of Barisal, after inspecting the latest batch of bodies recovered from the mangled heap of concrete.

Senior police officer Moshiuddowla Reza said at the disaster site that the death toll now stood at 273, and that most of those who died were female members of the complex's 3,000-odd workforce.

The collapse of the building in the town of Savar is the worst industrial accident in the country's history and is the latest in a spate of tragedies in the “Made in Bangladesh” clothing sector.

It prompted new criticism of Western brands who were accused by activists of placing profit before safety by sourcing their products from the country despite its shocking track record of deadly disasters.

Only British low-cost fashion line Primark and Spanish giant Mango have acknowledged having their products made in the collapsed bloc, while a host of brands including Wal-Mart and France's Carrefour are investigating.

The United States said it could not confirm whether any US companies such as Wal-Mart were sourcing garments from the complex, as protestors in San Francisco targeted the headquarters of Gap with banners reading “No More Death Traps”.

“But it does underscore that there's a need for the government, owners, buyers and labour to find ways of improving working conditions in Bangladesh,” deputy State Department spokesman Patrick Ventrell told reporters.

Last November a blaze at a factory making products for Wal-Mart and other Western labels left 111 people dead, with survivors describing how fire exits were kept locked by site managers.

The US Labor Department said it was working to help Bangladesh's government and workers' organisations address enforcement of building and fire codes.

Referring also to the November blaze, acting labor secretary Seth Harris said: “We must all — government, business and worker advocates — work urgently to help prevent such tragedies in the future.”

Hundreds of thousands of Bangladeshi workers walked out of their factories in solidarity with their dead colleagues on Thursday as flags flew at half mast and a national day of mourning was held.

Survivors said the building developed visible cracks on Tuesday evening, but factory bosses had demanded staff return to the production lines despite a police evacuation order.

“Those who're involved, especially the owner who forced the workers to work there, will be punished,” Prime Minister Sheikh Hasina told lawmakers.

“Wherever he is, he will be found and brought to justice.”