Two owners of garment factories in the building that collapsed on the outskirts of the Bangladeshi capital Dhaka have been arrested.
Mahbubur Rahman Tapas and Balzul Samad Adnan are suspected of forcing staff to work in the eight-storey building, ignoring warnings about cracks.
At least 336 people are known to have died after the Rana Plaza in the suburb of Savar collapsed on Wednesday.
On Saturday morning, at least 24 more people were rescued from the rubble.
Rescuers and volunteers, who worked through the night, cheered as they were brought to safety.
Earlier, rescue teams said they had located about 40 survivors on the collapsed third and fifth floors of the building.
Officials said they were working to extricate the remaining survivors and had passed oxygen cylinders and water to those still trapped.
Among those pulled out alive after three days in the rubble was Marina Begum, 22, now recovering in hospital.
"It felt like I was in hell," she said.
"It was so hot, I could hardly breathe, there was no food or water. When I regained my senses I found myself in this hospital bed."
More bodies of victims were also retrieved overnight and on Saturday morning.
Some 3,000 people are believed to have been working in the building at the time of the collapse and about 600 are still missing. Rana Plaza housed three garment factories, a bank and a number of shops.
Watching the operation are hundreds of relatives of those still missing, many clutching photographs of their loved ones.
Abul Basar wept as he awaited news of his wife who worked in one of the garment factories.
"My son says that his mother will come back some day, she must return," he cried.
Mr Tapas and Mr Adnan, the owners of the New Wave Bottoms and New Wave Style factories, were remanded in custody for 12 days by a court on Saturday. They were arrested earlier in the day after turning themselves in.
Deputy chief of Dhaka police Shyami Mukherjee said the two were accused of causing "death due to negligence".
The owners reportedly told their employees to return to work on Wednesday, even though cracks were visible in the building a day earlier.
Three other clothing factories were reportedly operating in the building.
Police are also questioning two municipal engineers who are reported to have approved the safety of the building a day before it collapsed.
The owner of Rana Plaza, Mohammed Sohel Rana, is said to have gone into hiding.
"Those who're involved, especially the owner who forced the workers to work there, will be punished," Prime Minister Sheikh Hasina told lawmakers on Friday.
"Wherever he is, he will be found and brought to justice," the prime minister added.
There is widespread anger in Bangladesh over the disaster and fresh clashes between police and protesters erupted again on Saturday.
On Friday, police used tear-gas and rubber bullets to break up crowds that had blocked roads, set fire to buses and attacked textile factories.
Protesters are demanding that the government arrests all those responsible for the disaster and improves conditions for garment workers.
Police are guarding other garment factories in the area.
Bangladesh has one of the largest garment industries in the world, providing cheap clothing for major Western retailers that benefit from its widespread low-cost labour.
But the industry has been widely criticised for its low pay and limited rights given to workers and for the often dangerous working conditions in garment factories.
Primark, a clothes retailer with a large presence in Britain, confirmed that one of its suppliers was on the second floor of the Rana Plaza, and said it would work with other retailers to review standards.
Labour rights groups say the companies have a moral duty to ensure their suppliers are providing safe conditions for their employees.
UK fashion designer Katharine Hamnett has called on fashion brands to insist on safer working conditions for garment workers internationally.
"The price of clothes may be low but they are paid for with human lives," she is reported to have said at the Vogue Festival in London on Saturday.
"We should demand credible, certifiable inspections on building structures and industry standards."
She added: "This is a very dark day for the clothing industry."
Meanwhile, the Bangladesh Communist Party and left-leaning Jatiya Samajtantrik Dal party have called a general strike on 2 May to demand punishment for those found responsible for the deaths.