A senior Treasury minister has described as "shocking" the conduct of nine HMRC staff sacked for underpaying benefits to ethnic minorities.
Exchequer Secretary to the Treasury David Gauke, who was in Northern Ireland on Thursday, said police were investigating the case.
Two resigned after an inquiry began at a Belfast call centre and seven were dismissed this week.
They are believed to have deliberately tampered with computer records.
Mr Gauke, said it was "utterly unacceptable that this behaviour has occured".
"It is absolutely right that HMRC took very strong action against the individual," he added.
All the people affected have now been fully reimbursed.
It is understood about 200 people work at the contact centre.
The allegations of racially-motivated gross misconduct were investigated last January when a complaint was lodged by somebody who said that their records had been changed.
A detailed audit was carried out and the inquiry then widened it to take in another 16 child benefit cases.
The HMRC contact centre is based at Dorchester House, close to the city centre in Belfast's Great Victoria Street.