MRS GERALDINE Gilligan and her son, Darren (22), and daughter, Tracey (23), were still being held in Lucan Garda station early today by detectives investigating the murder of the journalist, Ms Veronica Guerin.
Mrs Gilligan's husband, John, who is awaiting trial in Britain on drug-trafficking charges, has acknowledged he is suspected of ordering her killing but denies responsibility.
Gardai said Mrs Gilligan - and her two children were held under Section 30 of the Criminal Justice Act, which allows for detention of two successive periods of 24 hours.
All three were arrested on Tuesday morning.
New searches of Gilligan-owned property are expected to be carried out this morning, gardai said.
Last month, Mrs Gilligan won a High Court action which said she was not liable for a £1.6 million tax bill and that it was her husband, from whom she is estranged, who is liable to make a return to the tax authorities.
But the Criminal Assets Bureau, which brought the action, did not rule out the possibility of bringing further legal proceedings against Mrs Gilligan in respect of the equestrian centre at Jessbrook House, Enfield, Co Meath.
In a separate action, Mr Gilligan is challenging the constitutionality of the Proceeds of Crime Act 1996, enacted after the murder of Ms Guerin.
The Act established the Criminal Assets Bureau.
Judgment has been reserved in the action he is taking against the CAB, Mr Barry Galvin, Inspector of Taxes, and Chief Legal Officer, Mr Frank Lanigan, the Revenue Sheriff of Co Kildare, the Revenue Commissioners and the Attorney-General.
Giving evidence, the Deputy Garda Commissioner, Mr Noel Conroy, told the High Court that major criminals now had to work "on the "shopfloor" of their activities since the Proceeds of Crime Act came into force.
Mr Conroy believed the legislation was important for public confidence in the judicial system regarding criminal activities. In the last 10 years, criminals had switched from armed robbery and used their money to get involved in supplying drugs on a grand scale, using "runners" or couriers so they could distance themselves completely from their operations, Mr Conroy added.