The ombudsman has received a public complaint about how police dealt with the booby-trap bomb left for security forces at Kildrum Gardens in Creggan in August 1988.
Investigators will be at the Healthy Living Centre at Central Drive in Creggan to speak to anyone who may have information.
Sean Dalton, who was 55 and Sheila Lewis who was 60 were murdered by the bomb. Another man Gerard Curran died died the following year from his injuries.
Investigating officer Dunlop McCubbin said he believed people still had useful information.
"In particular I'm interested in a Datsun car which was abandoned at the rear of Kildrum Gardens on 25 August 1988," he said
"And I'm interested in what the police response was to that car being parked at the back of Kildrum Gardens. That car subsequently exploded in the early hours of 26 August.
"I'm looking for any information from the public about that car being abandoned."
Lost Lives, the book which chronicles every death in Northern Ireland's Troubles, said the incident was described as the "good neighbours bomb".
The IRA had kidnapped a man and booby-trapped his flat in the expectation it would be searched by the security forces.
Instead the three victims, who had noticed their neighbour's absence, went to the man's flat. Mr Dalton managed to get inside which detonated the bomb and demolished the flat.
According to Lost Lives Mr Dalton's family later claimed the police had been negligent in allowing civilians to approach the flat.
They allege the police were aware it had been booby-trapped but the bomb had been left in place to protect an informant.
The family stressed that the IRA was ultimately responsible for what happened but said the RUC should have also accepted its responsibility.
Investigators from the Police Ombudsman's Office will be in Londonderry on Thursday to appeal for information about the deaths of three people killed by an IRA bomb more than 22 years ago.