After trudging to every hospital and mortuary in Bangladesh's vast capital following last week's factory disaster, an exhausted Mohammed Jashim finally conceded defeat in his search for his beloved sister.

"For the last seven days, I think I must have walked literally hundreds of miles but it all seems to have been in vain as I've not been able to find her body," said the 25-year-old rickshaw driver.

"When you don't have money, all you can do is walk. But my tendons can't take it anymore."

Jashim's sister Jakiya Begum was one of an estimated 3,000 garment workers on shift at the Rana Plaza factory compound in a suburb of Dhaka which suddenly caved in on April 24 in the country's worst industrial disaster.

More than 2,400 people were rescued from the scene and 482 bodies have been pulled from the rubble so far.

But dozens more remain buried in the ruins and with bulldozers now scooping up giant piles of debris there is a very real possibility that some of the victims will never be traced.

Having been brought up by Jakiya after the death of his mother, Jashim feels a special bond towards his sister and a responsibility to find out exactly what happened to her in the April 24 tragedy.

The bodies of dozens of victims have not been identified, with authorities burying 32 of them in unmarked graves at a mass ceremony on Wednesday.

While accepting that his sister most likely died in the collapse in the suburb of Savar, Jashim had wanted to at least accord her a proper burial alongside other family members.

"I wanted her to rest in peace beside our mother," he told AFP while wiping away tears.

"I arrived at Savar last Thursday. Since then, it feels as if I have been doing nothing but crying and walking -- walking from one hospital to another, from the disaster site into the city and then back again."

Jashim began his labour of love after receiving a phone call from his brother-in-law Abu Kalam who told him that Jakiya was missing.

The mother of three children moved to the capital a decade ago after rising tides triggered by global warming submerged their farmland on an island in the southern coastal district of Barguna.

She found work as a seamstress at Rana Plaza where workers typically took home around 40 dollars a month, her meagre wages supplementing Kalam's income from his work as a rickshaw driver.

Bangladesh is the world's second largest garment producer, churning out clothing for Western brand names such as Walmart and Benetton at a fraction of the cost for which they appear on the shelves.

Whether touring the hospital wards or badgering rescue workers for information, Jashim always carries a laminated photo of his sister to help jog memories.

Scores of other relatives of the missing have also been camped out besides the ruins of Rana Plaza in similarly tragic vigils.

"I've visited 15 hospitals three or four times, but she was not among the injured," he said.

When he heard about Wednesday's mass burial of the 32 unidentified bodies, Jashim and his nephew Mohammed Helal dashed to the mortuary on another traumatic but ultimately futile mission.

"The stench of the bodies was so horrible that you felt vomiting. Some were in a decomposed state," he said.

"Even so, Helal and I examined each and every one of them, looking carefully at the bodies as my sister had a burns injury in her stomach and a big cut on her forehead."

None of the bodies resembled his sister.

Helal, 17, said he was similarly shattered -- physically and emotionally -- by the ordeal.

"I can't walk any more and I've cried so much that I don't have any more tears left," he told AFP back at the site of the disaster.