Pressure is mounting on gang members involved in planning and executing the abduction of businessman Kevin Lunney following the arrest of three people suspected of being on the fringes of the crime.
The three include a mother and son and another unrelated male.
The mother and son are thought to be related to an individual suspected of being involved in the kidnapping operation, while the other male is suspected of supplying a vehicle for the crime.
Garda sources said these arrests form part of a planned strategy to work towards the core members of the gang involved in surveillance for the kidnapping and the actual abduction.
It follows last week's search operation on both sides of the border and in England.
During those searches, the suspected chief organiser of the abduction, Cyril McGuinness, died after suffering an apparent heart attack when police entered what he had thought was a “safe house” in Derbyshire, in the East Midlands.
Police took away a quantity of potential evidence, including phones, computers and documentation.
That is being examined by the PSNI in a bid to identify any linkages, either in communications or transfer of funds to McGuinness from the “paymaster” of the campaign of intimidation against the directors of QIH.
McGuinness, a long-time crime boss with past links to the Provisional IRA, operated a variety of criminal enterprises along the border, including the theft of ATMs.
He lived in Derrylin, Co Fermanagh, the same home area of Mr Lunney. He and his gang associates were feared on both sides of the border.
Originally from north Dublin, and known as “Dublin Jimmy”, he is thought to have hired two criminals in the city in relation to the surveillance and kidnapping of Mr Lunney.
The father-of-six was abducted near his home on September 17 before being brought to a horse-box in Co Cavan where he was beaten and tortured and then dumped half-naked on an isolated road.
Following on from last Friday's search operation, which was specifically aimed at gathering evidence, gardaí conducted an arrest operation and picked up three people – a woman, aged 59, her son, 26, and another male, 48.
The two males were detained under Section 50 of the Criminal Justice Act 2007 in relation to the crime.
This anti-gang legislation allows for suspects to be detained for up to seven days on successive authorisations by senior officers and applications to the courts.
The woman is being held up Section 30 of the Offences Against the State Act.
Sources indicated that some of those arrested may not have expected it to happen and might not be prepared for spending up to seven days in custody.
Anything said by these individuals will be used by detectives to check against statements made by those more involved in the crime if and when they are arrested.
“These arrests put pressure on those further up, we're closing in on them,” said one source.
Gardaí will be monitoring the behaviour and communication of gang members following the arrests.