"We only wished it to be a warning to employers who fail to obey the law and who continue to underpay our members," the Southern African Clothing and Textile Workers' Union (SACTWU) said in a statement.
According the union, some employers were paying workers far below the government allowed weekly minimum rate of USD 43.74.
The union demanded "immediate compliance with the legally prescribed minimum wage".
South Africa has a relatively small textile sector, with firms are concentrated in the Western Cape and the eastern province of KwaZulu-Natal.
The mining sector and the public service are usually the hardest hit.