The Director of Public Prosecutions has reportedly concluded that there is not enough evidence to back claims that suspected Islamic militants are being illegally transported through Shannon Airport by the CIA.
Reports this morning said gardaí investigated three complaints relating to so-called CIA "torture flights" passing through Shannon and passed files on two of the investigations to the DPP.
However, the DPP decided not to pursue the cases due to a lack of evidence.
This morning's reports said details of the Garda investigation were contained in the Irish Government's submission to a Council of Europe investigation into the CIA flights.
The submission confirms that the use of Shannon Airport as part of the US programme of "extraordinary rendition" would be illegal and insists that no Irish officials have been involved in such activity.
It also reiterates assurances from the US authorities that Shannon is not being used as part of this programme, which the Council of Europe has said amounts to the effective "outsourcing" of torture.