A man and a woman disappeared Tuesday after a landslide swept their vehicles into a gravel pit dozens of metres deep.
Equipment and around 20 rescuers were lowered to the bottom of the quarry on Friday.
But technicians later warned the ground was too unstable to continue the operation and the site was evacuated.
Strong winds also prevented rescue crews from conducting their search Thursday at the quarry in L'Epiphanie, Que.
A third worker whose vehicle also fell into the quarry was rescued by a provincial police helicopter on Tuesday within hours of the collapse.