Gardai have now issued an appeal to anyone who may have spotted a car belonging to tragic Inishowen couple, Jimmy and Kathleen Cuddity, to come forward.
Gardai are keen to discover where the car was between 4pm on Wednesday afternoon and 9am yesterday morning.
The car is a silver Skoda Octavia, registration number 10 DL 274, was found at a lake outside Carndonagh yesterday morning.
Supt Eugene McGovern made the appeal for anyone who may have witnessed the Cuddity family car to come forward.
A 42 year old man is still being questioned in relation to the incident in which the couple were found dead at their home in Churchtown.
Gardai have until around 6pm to question, charge or release the man.
A hatchet was found at the scene.