Gardai will interview former senior employees of the Blood Transfusion Service Board as part of their investigation into the death of Mrs Brigid McCole from hepatitis C.
The investigation, conducted by the Garda National Bureau of Criminal Investigation under Chief Supt Sean Camon, has already begun.
The Garda Commissioner, Mr Pat Byrne, has ordered an investigation into alleged breaches of the criminal law, as detailed in letters he received from Mrs McCole's family and from Ms Jane O'Brien, chairwoman of Positive Action, the group representing women infected with the contaminated Anti-D.
The letter from the McCole family is understood to deal exclusively with her death in 1996, while Ms O'Brien's correspondence is believed to include other allegations of breaches of the criminal law in the course of the hepatitis C scandal.
Garda sources said last night the investigation "starts from scratch" and Mr Justice Thomas Finlay's report on the Tribunal of Inquiry will be used only as a guide. The report, which was subsequently sent to the DPP, will not form the basis of evidence in the Garda investigation. An earlier Garda investigation into the hepatitis C affair is understood not to have included interviews with former BTSB officials.
According to sources, "whatever resources are necessary" will be put into the criminal investigation but there is no estimate of how long it will last. In addition to interviewing former senior staff, the investigating gardai will visit a wide range of other people. Positive Action welcomed the decision by the Commissioner to conduct a criminal investigation into the contamination scandal.
Ms O'Brien said the group respects the independence of the Commissioner in this matter. "We acknowledge his action, in initiating an investigation which will be carried out by the Garda National Bureau of Criminal Investigation, results from a letter of complaint from the group and an individual letter of complaint from the family of the late Mrs Brigid McCole," she said.
The Commissioner's decision to proceed with a criminal investigation was welcomed in political circles.
The health spokeswoman for Democratic Left, Ms Liz McManus, said "it was long sought by the women who suffered so much".