Two journalists - arrested in connection with the suspected theft of confidential documents belonging to the Northern Ireland police watchdog - have been released on bail.
Trevor Birney and Barry McCaffrey worked on the documentary 'No stone unturned' - about the 1994 Loughinisland Massacre in Co Down.
It examined claims of state collusion in the loyalist murders and publicly named what it said were suspects.
Speaking after their release McCaffrey said the arrests should come as a warning to other journalists.
"It's not fair and it's an attack on the press, everybody should realise. It’s us today, tomorrow it could be you.”
Six men were murdered when loyalists opened fire on a crowd of football fans gathered around a TV in a pub in Loughinisland watching the Republic of Ireland play in the World Cup.
Last year’s No Stone Unturned documentary examined the persistent claims of state collusion in the murders and broke new ground by publicly naming what it said were suspects.
Police said the confidential material under investigation had been in the possession of the Police Ombudsman for Northern Ireland (PONI).
A police spokesman has claimed the theft of the documents “potentially puts lives at risk”.
PONI officers reported the alleged theft to the Police Service of Northern Ireland (PSNI).
The PSNI then asked Durham Police to conduct an independent investigation into the claims.
Flanking his client outside the police station, Mr McCaffrey’s lawyer John Finucane said he was “deeply disturbed” by the men’s detention.
Mr Birney’s solicitor Niall Murphy said a High Court challenge by the film company behind the documentary had injuncted the police from examining the evidence seized until the matter was aired at a full court hearing.
It is understood the custody interviews involved officers from both the PSNI and Durham Police.
Mr McCaffrey walked out of the police station carrying a book about Nelson Mandela.
While the men were held in Belfast, in Loughinisland families and supporters of those killed in the massacre staged a vigil in solidarity with the journalists.
Loughinisland vigil for arrested journalists Barry McCaffrey and Trevor Birney. Emma Rogan said the families of those killed in the Loughinisland massacre were shocked by the arrests this morning. pic.twitter.com/YX8ISyDXuT— Rebecca Black (@RBlackPA) August 31, 2018
Around 100 turned out to the Heights Bar for the demonstration.
Several held aloft a banner calling for justice for the atrocity and others held framed photographs of their murdered loved ones.
Emma Rogan, whose father was killed in the shootings, said the village was left stunned on Friday morning when they heard about the arrests.
“The whole community were shocked to hear they were arrested while the perpetrators of this heinous act have never been charged,” she said.
The attack unfolded on June 18 1994 when loyalist gunmen burst into the Heights Bar and opened fire on customers.
The UVF gunmen struck as football fans watched the Republic of Ireland team play in the 1994 Fifa World Cup.
In 2011, the Police Ombudsman Al Hutchinson found there had been major failings in the police investigation following the shootings, but said there was no evidence that officers had colluded with the UVF.
However in 2016, a new Ombudsman Dr Michael Maguire found there had been collusion, and the police investigation had been undermined by a desire to protect informers.
In 2017, a judge delivered a damning judgment against Dr Maguire’s report, ruling that he had exceeded his statutory powers by declaring officers guilty of colluding in the UVF attack.
Another judge is now presiding over a case that will focus on whether Dr Maguire’s findings should be formally quashed.
PA & Digital Desk