The UK’s largest sandwich-making factory, based in Bromley-by-Bow , could be fined more than half a million pounds if found guilty of knowingly employing illegal immigrants.

Immigration officers raided Greencore and arrested 32 workers as part of a Home Office crackdown.

Mail Online reported that during the operation workers were caught allegedly attempting to get rid of counterfeit identity documents and contacting friends to tell them not to come to work.

As a result of the raid groups of workers from Eastern Europe and Africa were arrested, with nine charged with immigration offences and remanded in custody.

One was bailed pending further enquiries. The fate of the remaining 22 is still being decided, but they could all be deported “if appropriate”.

The sandwich-making giant, which supplies Waitrose, Sainsbury’s, Morrisons and Asda, and its recruitment agency could be fined up to £20,000 per worker (a possible £640,000) if it is found that they did not check employees’ documents correctly.

A Greencore spokesman said: “Greencore closely follows the Home Office’s guidelines and goes to great lengths to try to ensure that all of our employees fulfil the necessary criteria to work legally in the UK.

“There have been numerous occasions in the past on which we have spotted suspicious applications and notified the immigration services immediately.

“We are determined to keep pace with the increasingly high quality of false documentation that is being produced and will do everything that we can to ensure that this kind of incident does not recur in the future.”

A spokesman for agency Prime Time Recruitment, which supplies Greencore, said: “Prime Time Recruitment wholly refutes any claims that it has employed illegal workers at the Greencore Bow factory.

“Prime Time is strictly and routinely audited to ensure all legal procedures are adhered to.