Rescuers are frantically searching for survivors after at least 175 workers were killed and hundreds more injured when an eight-storey complex, housing a factory that supplies British firms, collapsed in the Bangladeshi capital.

Hundreds of people were believed trapped in the concrete rubble of the building that collapsed in Bangladesh one day after workers complained cracks had developed in the structure. The death toll jumped yesterday after searchers worked through the night.

"The death toll could go up as many are still trapped under the rubble," district police chief Habibur Rahman said.

Searchers tore holes in the jumbled mess of concrete with drills or their bare hands, passing water and flashlights to those pinned inside the building near the capital Dhaka.

"I gave them whistles, water, torchlights. I heard them cry. We can't leave them behind this way," said fire official Abul Khayer.

Rescue operations illuminated by floodlights continued through the night.

Survivors said that thousands of workers and residents were inside the Rana Plaza building when it collapsed, but only 600 had been rescued on the first day.

New Wave Style, a garment factory which occupied three floors of the building, reported that women comprised at least half the casualties and many children were also victims. The company provided creche facilities for the children of its female workers on the second, sixth and seventh storeys.

As early as Tuesday, cracks were noticed in the structure of the building. Bangladesh's Industrial Police confirmed they had ordered the evacuation of Rana Plaza, but thousands of people nonetheless reported for work on Wednesday. Some said they returned to the factories on pain of dismissal after engineers working for the building's owner inspected the structure and pronounced it safe. Some workers returned to their sewing machines just an hour before the complex collapsed.

Buildings in Bangladesh are often shoddy constructions, built with little regard for strength or safety.

All the upper floors of Rana Plaza collapsed, leaving only the ground floor intact. Four garment factories occupied six of the eight floors.

New Wave Style, the largest of the factories, lists international retailers such as Benetton along with British high street names such as Primark, Matalan and Bonmarche among its main buyers.

Benetton denied that "people involved in the collapse of the factory" were its suppliers.

One survivor, Shaheena Akhter, 23, said that she and her colleagues had returned to work only after being threatened with dismissal.

Sobbing and anxious to resume her search for missing friends, she said: "Some of us did not want to work fearing something might happen, but the garment factory people told us that we had to join our work otherwise we will lose our jobs.

"We started working and around 9am the building collapsed.

"Somehow I managed to leave the building. I really am not sure how. I was inside the building and somehow I managed to get out. I can't describe it. God saved me, somehow how I managed to escape," she said.

- Telegraph Group Ltd