Police and immigration enforcement officers arrested 13 Indian nationals during a raid at a factory in England's Leicester city earlier this month, an official statement said on Thursday.
The statement issued by immigration advice site, workpermit.com, said that 11 of the migrants remain in custody, while the other two have been released on the condition that they report regularly to Home Office officials. The arrests were made on June 4.
Officials also stated that they seized money as well as employment documents.
If it is found that the men were working illegally, a fine of 20,000 pounds ($30,929) will be imposed on each migrant.
"This was a large scale operation targeting suspected immigration abuse in Leicester. Our investigations will continue with the evidence we have seized. Employers who flout the law will not be tolerated," a senior immigrant official said.
"Illegal working is unfair on honest employers and takes jobs away from those with a legal right to work."
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According to official data, in 2014 over 14,000 arrests were made, compared with approximately 7,500 in 2011.
Last year, the Home Office doubled the fines they can levy against employers of undocumented migrants, from 10,000 to 20,000 pounds per worker.