Three floors of the eight-story building apparently were built illegally.
A garment manufacturers' group said the factories in the building employed 3,122 workers, but it was not clear how many were inside when it fell. About 2,500 survivors have been accounted for.
Army Maj. Gen. Chowdhury Hasan Suhrawardy, the coordinator of the rescue operations, said the next phase of the search involved the heavy equipment such as hydraulic cranes that were brought to the disaster site Sunday. Searchers had been manually shifting concrete blocks with the help of light equipment such as pickaxes and shovels, he said.
The work will be carried out carefully so as not to mutilate bodies, he said. "We have engaged many private sector companies which supplied us equipment, even some heavy ones," Suhrawardy said.
In a rare bit of good news, a female worker was pulled out alive Sunday. Rescuer Hasan Akbari said when he tried to extricate a man next to the woman, "he said his body was being torn apart. So I had to let go. But God willing, we will be able to rescue him with more help very soon."
The collapse and previous disasters in garment factories have focused attention on the poor working conditions of workers who toil for as little as $38 a month to produce clothing for top international brands.
The death toll surpassed a fire five months ago that killed 112 people and brought widespread pledges to improve worker-safety standards. But since then, very little has changed in Bangladesh.
Its garment industry was the third-largest in the world in 2011, after China and Italy, having grown rapidly in the past decade.
Among the garment makers in the building were Phantom Apparels, Phantom Tac, Ether Tex, New Wave Style and New Wave Bottoms. Altogether, they produced several million shirts, pants and other garments a year.
The New Wave companies, according to their website, make clothing for several major North American and European retailers.
Britain's Primark acknowledged it was using a factory in Rana Plaza, but many other retailers distanced themselves from the disaster, saying they were not involved with the factories at the time of the collapse or had not recently ordered garments from them.
Wal-Mart said none of its clothing had been authorized to be made in the facility, but it is investigating whether there was any unauthorized production.