According to reports, the authorities received valuable new information that has led them to conduct an investigation in woodland, in a remote area of County Laois.
They are now carrying out a dig in the area, after reportedly receiving vital information from a potential witness.
Hairdresser and part-time model Fiona was seven months pregnant when she disappeared at 6am on August 22nd, 1996, from her home in Tullamore.
Police believe that the 25-year-old was murdered, but subsequent searches have failed to turn up any evidence.
The new search comes after Gardaí undertook a full review of the case over the past 12 months, reinvestigating their suspects and evidence.
It emerged this week that the main suspect, a man in his 40s, was taken into custody while travelling abroad.
