A fire broke out in the ruins of a Bangladeshi factory on Sunday, dashing hopes of rescuers to save a woman, believed to be the last survivor after struggling for life for more than 100 hours pinned underneath the rubble.

Rescuers were working to lift concrete slabs to get to the woman, a worker at the garment factory, when the blaze erupted. Fire fighters managed to douse the flames in a matter of minutes, but the woman was already dead, fire chief Ahmed Ali told AFP.

“She was a brave lady and fought until the end. We worked for 10-11 hours today to try to bring her out alive. We took the challenge but we lost,” he said. Three rescuers were also injured in the fire.

More bodies are expected to be found as workers, who had been digging manually to avoid harming survivors, switched to using earth-moving equipment to lift slabs and reinforced concrete after the eight-storey Rana Plaza collapsed Wednesday, claiming 381 lives, according to AFP. Thousands have been rescued from the wreckage, with some undergoing amputations to free them.

The owner of the building, Sohel Rana, was arrested earlier on Sunday as he tried to leave the country and cross into India. Two other factory bosses and two engineers were also detained by authorities.

The incident highlights the unsafe working conditions for Bangladesh’s garment workers, who are among the world’s lowest paid despite their industry’s rapid growth, says the Financial Times.