The 16 Indian nationals were arrested in July during raids at two factories, a restaurant and shop in the West Midlands and two restaurants in Lanarkshire, Scotland.
Action is now being taken to deport them to India. Also, 25 Bangladeshi nationals were arrested in July for working illegally in restaurants in West London, Warwickshire, Surrey, Oxfordshire and Herefordshire. Action is underway to return all of them to Bangladesh.
"We are cracking down on companies that employ illegal workers and fail to carry out proper checks on passports and other identity documents," a UK Border Agency spokesperson said.
"Any business that takes on a foreign national without permission to work is breaking the law and faces a heavy fine and possible prosecution," the spokesperson said.
A fine of up to 10,000 pounds will be imposed on employers for every illegal worker found in their business, unless the employers can prove that they carried out the correct right-to-work checks on the employees.
The UK Border Agency has also been working with local Sikh community leaders and Gurudwaras in the West Midlands to provide advice to migrants, some of whom are destitute, and wish to return to India.
The monthly advice centres are being held at the Gurdwaras in Smethwick; Sedgley Street, Wolverhampton; High Street, West Bromwich; Soho Road, Handsworth, Birmingham and Foleshill Road, Coventry.