The London Evening Standard reports that the scam is said to based on tax relief for bogus charitable donations.
A fraud investigation team from the Inland Revenue questioned the workers about the scam which has allegedly been running for some while.
The sum involved could be as much as £2 million.
It came to light after the Inland Revenue began investigations into certain aspects of allegations of racial harassment and bullying by production line employees last year.
Report argues that the government must change the way it makes tax and budget decisions
Drastically fewer offices for HMRC in the hope to reduce their running costs
Tayabali Tomlin and d&t directors launch £20 a month TaxGo service, aiming to be the 'biggest UK firm' by client numbers
Companies must report on their complex financial structures including offshore accounts and notify HMRC