A computer has been seized from a woman who received personal details of every Belfast city councillor.
Heather M Brown surrendered the computer at her home in England under the terms of an order secured at the High Court in Belfast.
The personal information was mistakenly emailed by a member of staff at Belfast City Council following a request for contact details.
It contained private phone numbers and bank details.
National insurance numbers, car registrations and some passport details were also disclosed.
A judge also authorised the recovery of electronic storage devices or any hard copies of the spreadsheet.
Experts are now to examine the computer, delete the information from it and attempt to trace any location it may have been forwarded on to.
It was claimed in court that a copy has already been sent to Justice Minister David Ford's office, in breach of an injunction against further disclosure granted earlier this month.
The court heard Ms Brown used the pseudonym of Prudence Halliwell - also the name of a fictional witch in the television series Charmed.
An Anton Piller order permitting council representatives to enter Ms Brown's home - believed to be in the London area - and seize relevant material was granted last week.
However, details could not be reported until enforcement was carried out.
It involved a supervising solicitor retrieving the computer for inspection by an IT expert.
During the application City Council barrister Keith Gibson acknowledged: "It's a draconian order granted in fairly limited circumstances where there is a very real danger."
The judge who heard the request, Mr Justice Stephens, stressed that Ms Brown must be fully informed of her right to participate in the proceedings.
He added that she should be offered a substitute computer while her own equipment is being examined.
In court on Wednesday Mr Gibson confirmed that Ms Brown surrendered her computer on Tuesday.
"Thankfully it does not appear that there was any enormous resistance to the order," he said.
"She wasn't terribly pleased, but (there was) nothing that would cause any public order concerns."
The council's legal representatives are now waiting for a report on the computer's contents before deciding their next move.
In a statement, the council said it regretted both the release of personal information and having to take action to prevent its further use.
"The council attempted to recover the data on a voluntary basis but was unable to do so," it said.
"It was therefore compelled to take legal action to prevent any further dissemination given the personal nature of the data in question."
The statement added: "The protection of personal data is very important to the council which is reflected in the steps taken in this case.
"The council is currently reviewing the systems and procedures that already exist to ensure as far as practicable that the risk of human error is minimised and that security is maintained."