At least eight men and a woman have been arrested in raids connected to four allegedly bogus language colleges.
The raids by 80 police officers and immigration officials in London also targeted the homes of those suspected of operating an immigration racket.
The racket, thought to involve a solicitors' firm, allegedly helped many people settle illegally in the UK.
Officials believe they would have enrolled at one of the colleges, then applied for student visas.
The firm of solicitors is suspected of issuing false education certificates which would enable the immigrants to obtain visas.
Raid on the home of an immigration racket suspect
Fears about bogus colleges have been growing in recent years.
Back in January, almost half the colleges checked on an official list of approved providers for overseas students were struck off.
The approved register was created in 2005 to prevent abuses such as visa scams and required applicants for student visas to show that they would be attending a legitimate institution.
The raids are part of a wider crackdown on immigration which has been running since February.
Since then 65 employers have been prosecuted for hiring illegal immigrants and faced fines totalling �2.3bn.
Home Secretary Jacqui Smith met officers before the operation, on the day she launched the new strategy to enforce immigration laws and catch offenders.
This includes naming and shaming companies who employ illegal immigrants.
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