More than 20 bodies were pulled from the rubble of the Rana Plaza building in Savar overnight, bringing the total to 501, the army said.
The building contained five clothing factories and scores of workers are still unaccounted for.
Nine people, including the building’s owner, have been arrested.
Excluding the terror attacks on the World Trade Center in New York, the deadliest industrial structural failure in modern times was the Sampoong department store collapse in Seoul, South Korea, in 1995, that cost the lives of 502 people.
Late on Thursday, Bangladeshi police arrested another engineer in connection with the disaster.
They say Abdur Razzak Khan acted as a consultant for Rana Plaza owner Mohammed Sohel Rana, who is suspected of illegally adding more floors to the building.
Bangladeshi media reported that Mr Khan had been called to inspect the building after it developed cracks the day before the collapse on 24 April.
Two other engineers are also in custody, along with Mohammed Sohel Rana and the owners of garment factories that occupied the building.
No survivors have been found in the past four days but many relatives are still waiting at the scene for news of their loved ones. Officials say 2,437 people have been rescued from the building following its collapse.
Rescuers say they do not know how many people are still missing as factory owners have not given them precise figures.
On Thursday, garment factories across Bangladesh reopened for the first time since the collapse last week.
Workers had been holding daily protests demanding tough punishment for those responsible and better factory safety standards.