Five Indian immigrants working illegally in a factory in the east Midlands town of Leicester have been arrested.
Officers from the UK Border Agency swooped on Sunnyville Clothing's factory last week and sealed all exits before questioning workers and checking identity documents.
Five men from India were questioned and arrested after they were found to be working illegally.
Gail Adams, regional director for the agency, said, "We are working hard to pull the plug on the illegal jobs which lure illegal immigrants to the UK in the first place.
"Illegal working is unfair on honest employers who recruit staff with the right to work in the UK and who pay them a proper salary.
"Employers which don't play by the rules will get struck off our register, lose the right to recruit staff from outside Europe, face on-the-spot fines and could, potentially, end up in jail."
To avoid a heavy fine, any employer which falls under suspicion must convince the UK Border Agency that it carried out the correct checks for employing workers from outside the EU.