The death toll from the collapse of an eight-storey factory building near the Bangladeshi capital, Dhaka, has passed 500, officials say.
Another 29 bodies were pulled from the rubble of the Rana Plaza building in Savar overnight, bringing the total to 507, the army said.
Scores of workers are still unaccounted for. Nine people have been arrested.
It is Bangladesh's worst industrial disaster and has sparked anger among workers in the country.
The previous most deadly structural failure in modern times - excluding the 9/11 terror attacks in New York - was the Sampoong department store in Seoul, South Korea, in 1995, in which 502 people died.
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.
Correspondents say the arrest came as a surprise, as Mr Khan was the engineer who had warned that the complex was unsafe.
Bangladeshi media reported that he had been called to inspect the building after it developed cracks the day before the collapse on 24 April.
He appeared on a private TV station saying he had told the owners to evacuate the building because it was not safe, according to the reports. He said he had told government engineers that the building should be examined further.
Two other engineers are also in custody, along with the building's owner Mohammed Sohel Rana, his father Abdul Khalek and four owners of garment factories that occupied the building.
Officials say about 2,500 people were injured in the collapse and that 2,437 people have been rescued.
No survivors have been found in the past four days but many relatives are still waiting at the scene clutching photographs of their loved ones.
One woman, named only as Bulbila, said she was still waiting for news of her daughter.
"The name of my daughter is Mallika. She was working in that factory on the fourth floor, she joined three months ago, there's no trace of her as yet," she said.
Many bodies that were badly damaged and decomposed beyond recognition have gone unclaimed and have already been buried, officials say.
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.
There were violent clashes with police and some factories had to be placed under guard.
Bangladesh has one of the largest garment industries in the world, and some of the clothes produced in the building were made for Western retailers.
The EU has said it is considering "appropriate action" to encourage an improvement in working conditions in Bangladesh factories.
It said its actions may include the use of its trade preference system, which gives Bangladesh duty- and quota-free access to EU markets.