More dead were also discovered. Shamim Islam, a volunteer who entered the collapsed building along with rescue workers, said he saw "many bodies inside."
Search crews were cautiously using hammers, shovels and their bare hands. Many of the trapped workers were so badly hurt and weakened that they needed to be removed within a few hours, rescuers said.
There were fears that even if unhurt, the survivors could be badly dehydrated, with daytime temperatures soaring to 35 degrees Celsius (95 degrees Fahrenheit) and about 24 degrees Celsius (75 degrees Fahrenheit) overnight.
Nearly 90 people have been rescued in the last day, as hundreds of rescuer workers crawl through the rubble amid the cries of the trapped and the wails of workers' relatives gathered outside the building.
A garment manufacturers' group said the factories in the building employed 3,122 workers, but it was not clear how many were inside it when it collapsed Wednesday in Savar, a suburb of Bangladesh's capital, Dhaka. Rescue officials say more than 2,400 have been rescued or escaped.
Police cordoned off the site, pushing back thousands of bystanders and relatives after rescue workers complained the crowds were hampering their work.
Clashes broke out between the relatives and police, who used batons to disperse them. Police said 50 people were injured in the skirmishes.
"We want to go inside the building and find our people now. They will die if we don't find them soon," said Shahinur Rahman, whose mother was missing.
Thousands of workers from the hundreds of garment factories across the Savar industrial zone and other nearby areas marched to protest the poor safety standards in Bangladesh. Local news reports said demonstrators smashed dozens of cars Friday, although most of the protests were largely peaceful.
Police say they ordered an evacuation of the building on Tuesday after cracks in Rana Plaza were found, but the factories ignored the order and were operating when it collapsed the next day. Video before the collapse shows cracks in walls, with apparent attempts at repair. It also shows columns missing chunks of concrete and police talking to building operators.