A Cabinet Minister says phone conversations were recorded digitally at Garda stations after 2008.
According to Simon Coveney, 2,400 physical tape recordings exist of phone calls prior to that date, but digital recordings were made after that until the practice was stopped last year.
He says he doesn't know how many were recorded after 2008, or who was listening to them.
It has also emerged that the Attorney General did not attend yesterday's Cabinet meeting, after which the commission of inquiry into the recordings was announced.
Meanwhile, Minister Coveney says tapes are in the process of being handed over in an ongoing court case, and he says some of the detail on those recordings is "very explosive".