Four Brazilians face imminent deportation after they were caught working illegally on farms.
Sussex Police and immigration officials arrested 18 suspects after setting up a roadblock on the outskirts of Chichester.
Of those, 14 are still being questioned by the immigration service.
Officers made the arrests at dawn yesterday in a joint operation by police, the immigration service and the Vehicle and Operator Standards Agency.
The suspects are believed to have been on their way to work at farms in the Chichester area and were arrested at Hunston, south of the city.
A spokesman for the immigration service said: "Following the arrests, four Brazilians were found to be working illegally and without permits.
"They will be removed from the United Kingdom immediately.
"We are still questioning 14 others arrested in the joint operation. If any are found not to have work permits, they will also be removed.
"We will not tolerate people working illegally in this country."
Officers acting on information targeted vehicles carrying workers to local farms for their daily shifts.
Police officers flagged the vehicles down while immigration officials interviewed those being carried inside.
Interpreters were on hand to overcome language barriers.
Officials from the Vehicle and Operator Standards Agency checked the vehicles and documentation.
Ten vehicle defects were found.
The operation was co-ordinated by the West Downs road policing unit, based at Chichester, and support teams.
Last year, 94 Brazilians were flown home from Gatwick after they were caught working illegally at a biscuit factory in Esher, Surrey.
They had to fly back in small groups after the Brazilian government denied permission for a plane carrying them all to land.
Officials in the country's ministry for foreign relations caused the planned flight from Gatwick to be abandoned after informing the Home Office it would refuse to allow a plane carrying the deportees to touch down.
They said it would be humiliating for them all to land together and demanded they be transferred to scheduled flights where their privacy would be better respected.
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