Two men were arrested after a swoop on a Hemel Hempstead town centre chicken shop on Tuesday afternoon.
Immigration officers acting on a tip-off found two Sri Lankan workers at Crazy Chicken in Marlowes were breaking the rules.
A 26-year-old man was a failed asylum seeker and a 19-year-old colleague was in breach of visa conditions.
They are now in detention and are likely to be kicked out of the country.
The shop could also face a fine of up to £10,000 for each worker unless it can prove it carried out proper checks before taking them on.
Chris Evans, from Home Office Immigration Enforcement, said: “Operations like this are carried out across the UK every day as we continue our work to track down and remove from the country those who seek to abuse our immigration laws.
“The public can be a huge help and I urge people with information about suspected immigration offenders to get in touch.”
Anyone with information about immigration crime can contact Crimestoppers on 0800 555 111 anonymously or click here