Police said it was too dangerous to search overnight, and began again Wednesday at 7 a.m.
The Canadian Broadcasting Corp. said helicopters, trained rescue workers and dog teams were taking part in the search.
Crews were able to see inside the cabin of one truck that tumbled down the rock face after the Tuesday morning landslide, but it was empty, CBC said.
Rescuers had not been able to reach the second truck's cabin.
The quarry, located in I'Epiphanie, belongs to Maskimo Construction Inc., and the missing workers are subcontractors employed by Allard G. Excavation Inc., CBC reported.
The victims' identities had not been released but they were described as a man and woman in their 40s, police said.