ILLEGAL immigrants were arrested in a series of raids across Huddersfield.
Officers detained 16 people in swoops on houses in Oakes, Aspley, Milnsbridge, Birkby and Elland.
Six of the offenders had entered the UK illegally, nine were failed asylum seekers and one had overstayed his visa.
Four were also suspected of possessing false identity documents.
The joint operation by the Border and Immigration Agency and West Yorkshire Police took place on Monday and Tuesday but details were released only yesterday.
It was part of intelligence-led moves to tackle illegal employment and the use of false identity documents.
Immigration officials said they were seeking to expel all 16 from the UK.
Chris Hudson, regional director of the Border and Immigration Agency, said: "Border and Immigration Agency staff are working hard across our region to target illegal working and remove failed asylum seekers and other immigration offenders.
"To combat illegal immigration it is not enough to stop illegal journeys.
"We have to close down the illegal jobs that tempt people to come to Britain.
He said the Identity Cards Act 2006 was being used successfully to target illegal working and immigration offenders.
Thirty arrests have already been made across the region using the new powers.
Mr Hudson said: "This operation is just one example of the work carried out every week and it is essential the local community know this work is being done."
Chief Supt Barry South, divisional commander for Kirklees, said: "West Yorkshire Police will continue to support operations such as these to combat identity fraud and illegal working.
"This operation should send out a clear message that possessing and using false documents to gain employment in this country is illegal and the police will support action to trace and deal with those we suspect of committing such offences."