A Cantonese restaurant which may face fines of up to £40,000 following an immigration swoop was also raided two years ago as part of an illegal working operation, officials have confirmed.

Kitchen workers at Tam’s Cantonese Cuisine in Cross Hills, near Keighley, were arrested when immigration officials from the UK Border Agency raided the premises last week.

The employers of the four people who were searched and arrested at the scene could be hit with fines of up to £10,000 for each of those arrested and the kitchen workers, suspected of working there illegally, could be deported.

It has now emerged that two Chinese nationals were arrested during a previous swoop in 2007, but their employers escaped a fine because new immigration laws had yet to come into force.

A spokesman for the UK Border Agency said the two workers who had been arrested in the 2007 raid had not yet been removed from the country as checks into their backgrounds were still on-going.

Spokesman Richard Shrubb said: “The operation in 2007 was conducted before the introduction of the tough new civil penalty system – the notification of potential liability – as a deterrent to employers, so there were no fines issued.”

In the latest raid, immigration officials wearing body armour searched the restaurant before taking away four people, understood to be failed asylum-seekers, in a van. Two men, aged 36 and 44, and a 27-year-old woman, were taken into custody.

Another 25-year-old man, who was already reporting to the UK Border Agency, will have his case reviewed.

Mr Shrubb said the agency was unable to provide “specific information” on the two workers arrested in the previous raid.

But he confirmed: “Tam’s Cantonese Cuisine was previously visited by UK Border Agency officers on November 7, 2007, as part of an illegal working operation.

“As a result of the operation, two Chinese nationals were arrested. We have been unable at this stage to enforce removal for these two individuals so are not able to give more specific information on their cases.”

A spokesman for Tam’s said: “We are still waiting for the letter from the immigration agency so, at this moment, there’s nothing we want to add.”

e-mail: marc.meneaud@telegraphandargus.co.uk