The owners of Spanish fashion chain Zara say they are strengthening the oversight of their production system after workers were found toiling in a Brazilian sweatshop.
A raid in Sao Paulo found mostly Bolivian immigrants working for a pittance in unsafe conditions.
Inditex, the parent company of Zara, said it had zero tolerance for such infringements.
The workers were employed illegally by a subcontractor, Inditex said.
A raid in Sao Paulo found people working in cramped, unsanitary conditions, for long hours.
Electrical wires dangled dangerously from the walls above piles of fabric, says the BBC's Paulo Cabral, who accompanied officials on their raid.
The people were being paid between 12 and 20 cents a piece - the equivalent of 7-12 US cents (4p-7p), Brazilian media reported.
Inditex, the world's biggest clothes retailer, said 15 people had been found working in a factory for a subcontractor without their knowledge.
Upon learning of the case, Inditex acted immediately, a company statement said.
"The supplier has accepted full responsibility and is paying financial compensation to the workers as required by Brazilian law and the Inditex Code of Conduct," the statement said.
The supplier was also going to improve the subcontractors' working conditions to bring them in line with those at facilities audited and approved by Inditex inspectors, it went on.
Inditex has approximately 50 suppliers in Brazil, which employ more than 7,000 workers.
The company said it wanted to "foster the best conditions possible in the Brazilian textile industry".
There are hundreds of factories in Sao Paulo state, producing garments for Brazil's booming market, our correspondent says.
Recently the Brazilian authorities formed a special task force to locate and shut down sweatshops.
Many of the workers are smuggled into Brazil from Bolivia, said Luiz Alexandre Faria from the labour ministry.
"They can't leave the workshop until they pay for their journey. Some employers even confiscate the workers' documents," he told the BBC.
Brazil's criminal code classifies slave-like labour as instances including when a person is forced to work exhausting hours, subjected to an unsafe working environment and prevented or restricted in their movement to and from work.