Authorities said the family was in their basement cheering on the Montreal Canadiens in their Stanley Cup playoff ice hockey game against the Pittsburgh Penguins when the massive landslide hit Monday night in Saint-Jude, a town of 1,000, near the Yamaska River.
"After digging and going through the rubble we found the four victims," Michael Dore, Quebec's emergency management co-ordinator, said Tuesday night. "They were found very close to one another, some of them lying on the couch in the family room in the basement."
The first body found belonged to father Richard Prefontaine. The others were his wife Lynne Charbonneau and daughters Anais, 9, and Amelie, believed to be 11.
The landslide tore a hole more than four times the size of a football field into Saint-Jude, a verdant village near Montreal.
Sinkholes can occur when water undermines an area of land or when rock below the land surface shifts.
This particular sinkhole ate up three cars, one stretch of a concrete road and most of the house that once sat by a cliff over a tributary of the Yamaska River. The landslide pulled down that cliff.
Rescue workers struggled for almost a full day - at times digging with their hands - to enter a home that was mostly buried in mud with only its green roof left peeking out.
"It's a pretty gigantic crater," said Francois Gregoire, a fire department spokesman. "It's hard imagining something like this. It's pretty impressive."
The family's lush green yard was transformed into an undulating mess of tangled trees, grass and clay blocks.
Mayor Yves de Bellefeuille said the incident had the small village in shock, especially since the home is not in an area considered to be especially at risk.
The St. Lawrence and Ottawa valleys are laden with clay deposited in low coastal areas during the last Ice Age.
The clay is very sensitive and, if disturbed, it can lose its physical strength and liquefy, causing its slope to collapse and the land to slide.
Natural Resources Canada said clay earthflows have caused 100 deaths in modern times, including the destruction of two Quebec towns - Notre-Dame-de-la-Salette in 1908 and St-Jean-Vianney in 1971.