An alleged immigration racket in Hounslow may have cost victims more than £300,000.
getwestlondon revealed in May how a man was arrested after more than 20 people claimed to have been defrauded out of tens of thousands of pounds.
Detectives investigating the case say they have now identified 30 potential victims.
Police were first contacted in December last year by a 28-year-old man who claimed to have handed over nearly £10,000 to man offering to advise foreign nationals wishing to remain in the UK for further education or work.
A Met spokesman said enquiries by officers from its Organised Crime Command team have identified a further 29 possible victims.
getwestlondon understands all the alleged victims claim to have paid a similar amount of money, which would make the total sum handed over around £300,000.
Man arrested on suspicion of fraud
A 34-year-old man was arrested in March on suspicion of fraud and has been bailed to a date in November.
Police, who had initially given the man's age as 35, said officers from the Met's Falcon fraud team are continuing to investigate.
getwestlondon understands all the alleged victims had been studying in the UK and had approached a company in Hounslow for help to remain in the country.
They say they were offered senior positions with firms listed on a government website as "tier 2" sponsors, whose backing would enable them to remain in the UK.
They claim they were asked by the immigration advisor they had approached to hand over around £10,000 each to cover his fees and the cost of training them for their new jobs.
But all their visa applications were rejected by the Home Office, they say, on the grounds the wrong codes had been entered, and they were offered no refund.