Divers, snowmobilers, ice rescue specialists, a drone and investigators are among the resources being mobilized in the area where the French tourists disappeared Tuesday.
Canadian authorities also released the names of the five French citizens and those of three others who survived the tragedy on Tuesday evening, as they were led by a Canadian guide.
The 42-year-old guide, Benoit L'Esperance, was pulled out by emergency response teams and taken to hospital, but later died.
Police said they were alerted by two of the tourists who had rescued a third from the water.
"All we can do in this situation of waiting and worry is to bring a little support to the family and loved ones", he said in a phone interview.
Snowmobile tours are an increasingly popular way to explore the Canadian wilderness.
The provincial force reported on its Twitter account Thursday evening that it had located four more snowmobiles submerged underwater near the same spot where two had previously been spotted by divers on Wednesday. The Quebec provincial government on Thursday said it wants to make training mandatory for guides and tourists who use snowmobiles.
Despite the crash yesterday of an SQ helicopter during the search that left its pilot injured, a second police aircraft and a Canadian Armed Forces helicopter will continue flyovers of the search area.
According to the French sports website l'Équipe, Gilles Claude was the father of two biathletes, Fabian and Florent, who competed in a biathlon event held in Slovenia on Thursday.
The group were not travelling along a trail marked for snowmobiling, say police, and ended up on very thin ice on a snow-covered channel near Lac St Jean when their vehicles went through the ice.
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Quebec Tourism Minister Caroline Proulx is expected to announce new measures for adventure excursions and ecotourism Thursday morning, including snowmobiles.