A bomb was left under the family car outside their home in Glenrandel two weeks ago.
Both husband and wife are serving police officers.
Police have arrested a number of people in Counties Donegal and Derry, seized various items and vehicles and searched properties in relation to the investigation.
Checkpoints were also set up in Eglinton early this morning as police continued their search for evidence in the investigation.
A leaflet with detailed appeal points was handed out to anyone who spoke to police.
Detective Chief Inspector Gareth Talbot, says there were quite a number of people out and about in the early hours of Thursday, 18 June in Eglinton.
And police want to ensure they have spoken to each and every one of them.
Police want to speak to anyone who saw individuals or vehicles in the Glenrandel area of the village between midnight and 3am on Thursday, 18 June.