Following a tip off, the UK Border Agency raided the New Forest Laundry, Hythe on 10 August and detained five workers on suspicion of illegal working.
Investigations are still continuing but unless a business can prove it carried out the necessary checks before employing staff who are then found to be working illegally, it can be fined up to £10,000 for each case,, with a maximum of £40,000.
Speaking after the raid a senior spokeswoman for the UK Border Agency's Hampshire Local Immigration Team, said: “Any employer who takes on a foreign national without permission to work in the UK is undermining law-abiding businesses and faces a big fine.
“This successful operation shows that our officers will find immigration offenders wherever they are and we carry out frequent operations to track them down.”
