St-Gelais won the women's race in two minutes and 24,532 seconds. The Saint-Felicien, Que., native finished ahead of Kim Boutin of Sherbrooke, Que. and Audrey Phaneuf of Boucherville, Que.
Taking advantage just before the last two laps, St-Gelais advanced from third place to win the race.
"I saw it develop right in front of me, so I was able to step in quickly and choose my spot," said St-Gelais, who has won six individual medals on the world cup circuit this season. "I'm satisfied with my race, I managed it well without losing too much energy."
Hamelin, a native of Sainte-Julie, Que., won the men's race in 2:13.564. Samuel Girard, of Ferland-et-Boilleau, Que., and Olivier Jean of Lachenaie, Que. finished second and third respectively.
"There was a lot going on (in the race)," said Hamelin. "The level was quite high in the final, with all seven skaters having the level it takes to win it. I mostly tried to stay away from trouble."
Hamelin has won four individual medals so far in the world cup season.