The Irish clothing chain Penneys has confirmed that one of its suppliers occupied part of the building that collapsed in Bangladesh.
At least 96 people died and more than a thousand were injured after a factory collapsed on the outskirts of the capital Dhaka.
A statement on the company's website said: "The company is shocked and deeply saddened by this appalling incident at Savar, near Dhaka, and expresses its condolences to all of those involved.
Penneys confirms that one of its suppliers occupied the second floor of the eight storey building, which housed several suppliers to the garment industry making clothing for a number of brands."
Penneys' parent company Primark said it has been engaged for several years with NGOs and other retailers to review the Bangladeshi industry's approach to factory standards.
It said it will push for this review to also include building integrity.
Firefighters and army personnel worked at the Rana Plaza building in Savar, 30km outside Dhaka, to rescue people trapped inside.
One fireman said that about 2,000 people were in the building when the upper floors jolted down on top of each other.
Bangladesh's booming garment industry has been plagued by fires and other accidents for years, despite a drive to improve safety standards.
In November last year, 112 workers were killed in a blaze at a factory in an industrial suburb of Dhaka.
A local police spokesman said factory owners appeared to have ignored a warning not to allow their workers into the building after a crack was detected in the block yesterday.
Five garment factories - employing mostly women - were housed in the building, including Ether Tex Ltd, whose chairman told Reuters he was unaware of any warnings not to open the workshops.
One witness said it looked like an earthquake had struck the area.
A factory worker said she was at work on the third floor when "suddenly I heard a deafening sound, but couldn't understand what was happening. I ran and was hit by something on my head".
Buildings in the crowded city of Dhaka are sometimes erected without permission and many do not comply with construction regulations.
Dozens died when a garment factory collapsed in the same area eight years ago.