A man already facing trial for serious crimes is at the centre of a Garda investigation into the theft of a batch of blank cheques from a Revenue Commissioners office.
Some of the cheques have been recovered by gardai, but the rest are "as good as cash" and could be made out for six-figure amounts, according to a senior Garda source.
It is understood the man had access to a Revenue Commissioners office while employed as a night guard by a large private security firm. He was not an employee of the commissioners.
Nineteen cheques went missing from the computer section in one of the Revenue Commissioners offices over a three-week period last month.
Six were seized by about 28 officers from the Garda Bureau of Fraud Investigation and the Kevin Street district who carried out dawn raids at seven houses in Dublin this week.
Recent unsuccessful attempts have been made to cash a further two of the cheques. One, made out for £286,583, was presented about three weeks ago at a London bank. Another, made out for £7,000, was presented at a bank in Ballyfermot, Dublin, within the past fortnight.
"We would be worried that there are still 11 cheques out there which could be negotiated for a six-figure sum," the source said.
The cheques are drawn on the accountant general at the office of the Revenue Commissioners at an account in the Bank of Ireland, College Green, Dublin. It is understood they are the kind used by the Revenue Commissioners to issue tax rebates and other payments.
Gardai say they are made of special paper with micro-printing and security features which would make it difficult to counterfeit them. All the missing cheques, which had serial numbers, have been stopped by the Revenue. But the Garda source said there are still worries the undetected cheques could be cashed if the serial numbers were changed. About half the stolen cheques had signatures.
"They are invaluable, as good as cash really if they can get them through the account," said the source.
Gardai described the man at the centre of their investigation as a "serial fraudster" in his late 20s. He is currently on bail on charges relating to theft and hijacking.
He was arrested following the Garda raids and later released without charge. Another man was arrested following the raids and is due to appear in court today.
A spokeswoman for the Revenue Commissioners said: "As a result of internal security checks it was identified that a small quantity of stationery was missing and the Revenue immediately initiated an internal investigation and a formal investigation by An Garda Siochana."
The spokeswoman stressed that none of the cheques had been cashed.