Immigration officers are continuing to question the suspected leaders of a gang that allegedly employed illegal foreign workers in a number of areas of England.
A major intelligence operation led to the arrests
The Home Office says three of those arrested in raids in West Sussex this weekend are thought to have run the operation.
A fourth person is being questioned on suspicion of forgery.
A further 38 people were detained in the raids on four houses in Littlehampton and a flower farm in Barnham, on Friday and Saturday.
The Home Office said any of those held who had been working illegally would be deported as soon as possible.
The operation was launched in the wake of an intelligence operation gathered in the summer when 60 illegal immigrants in Sussex were identified and expelled from the country.
'Government means business'
The Immigration Service (IS) said it hoped the "significant" arrests would help clamp down on illegal immigrant networks it said existed in other parts of the country.
IS spokesman: told BBC News: "It's very significant - this is, we believe, a group involved in large-scale facilitation and gang-mastering activities."
"They have contracts that we're aware of in at least four other counties - so we're pretty certain what is going on here may be replicated across the country."
Home Secretary David Blunkett said he hoped the raids sent out a message.
He said: "I want to congratulate all those involved in this significant operation.
"This should send a clear signal that we are getting ever-better at successfully
tracking down those behind the trade in illegal labour."
Home Office minister Beverley Hughes said: "We will take firm action not only against those who are working in the UK illegally but against the Mr Bigs - those further up the chain who accumulate vast wealth through supplying illegal labour.
"It is unacceptable that those who trade in human beings should reap profits and be able to live in luxury."
Action would be taken to take away any assets gained from any crime, she said.
A Home Office spokesman said any illegal workers would be removed from the UK as soon as possible.