Police have begun preparing a report on the 1972 Claudy bombing to be submitted to the Public Prosecution Service.
Nine people were killed in the no-warning bomb
Nine people, including three children, were killed when three car bombs exploded in Claudy, County Londonderry.
Four people held on Tuesday have been released without charge, including Sinn Fein's Francie Brolly and freelance sports commentator Seamus Mullan.
Mr Brolly said that he had nothing to do with the atrocity and had no foreknowledge of what would happen.
Mr Brolly said he believed he was arrested simply because he had been a republican living in the area at the time.
"Without going into any detail of how the interviews went, fundamentally, the only evidence, if you can call it that, they were putting forward for my possible knowledge of what happened in Claudy was that I live in Dungiven, which is 10 miles from Claudy. It was as ridiculous as that."
Mr Brolly said it had been a "character assassination" which had harmed himself and his family.
"When I read in the paper somebody has been released without charge, that doesn't impress me," he said.
"I'm asking: 'Why were they arrested in the first place?"'
Mr Brolly said the arrest had made him rethink his position within Sinn Fein as one of those moving towards an acceptance that policing in Northern Ireland had changed for the better.
The arrests were made on Tuesday morning.
A 58-year-old woman in Dungannon was one of those arrested.
All four were released without charge on Wednesday evening.
Police said a report was being prepared for submission to the Public Prosecution Service.
The service will examine the police report and assess whether there are sufficient grounds to merit a trial.
Mr Brolly is an assembly member for the East Londonderry constituency.
Seamus Mullan is a freelance journalist who reports on Gaelic games for a number of media outlets, including BBC Northern Ireland.
In December 2002, the police said a priest, who had died, was involved in the Claudy bombing.
It also emerged that both the Catholic Church's cardinal at the time, William Conway, and the then Secretary of State, William Whitelaw, met to discuss the matter.