The fire broke out near the tiny community of Kane, about 95 kilometres southwest of Winnipeg.
"The adults escaped. The three youngest children were saved by the mother. The four older children who were in the second level of a two-storey home perished in the blaze," said Ralph Groening, reeve for the RM of Morris.
Groening said volunteer fire crews unsuccessfully tried to put up a ladder to the second-floor window as the home burned.
"The fire was too far advanced. They were unable to go into the building. It simply wasn't safe."
Little remained of the 90-year-old farmhouse after the fire was out, although a storage shed 20 metres away and pine trees surrounding the blackened foundation appeared untouched by the flames.
Friends have identified the parents as Jake Froese and Doralee Eberhardt. Several local media outlets identified the four dead boys as Henry, Danny, Timmy, and Bobby. They ranged in age from nine to 15. People grieved their loss on Facebook.
Froese and an older son Steven both work at Tri Koating Inc., an industrial painting business in Winkler, Man., and were there when the fire started.
The municipality's volunteer fire chief, Bernard Schellenberg, said the father made the emergency call about 12:15 a.m. when he saw smoke as he and his son returned home.
About 20 volunteer firefighters from nearby communities responded in four trucks, said Schellenberg. The house was engulfed in flames and an addition that had recently been built had already collapsed when crews arrived.
Temperatures in the area were as low as -27 C with the wind chill over night.
"They went into a defensive strategy and they could not make entrance into the house due to heavy smoke and fire conditions," Schellenberg said.
The fire is under investigation by the Manitoba Fire Office and the RCMP, Schellenberg said.
The parents were receiving medical care and the surviving children were staying with friends, Groening said.
Tri Koating president Frank Krahn described Froese as a family man and said everyone's thoughts are with him and his family.
Pauline Lafond Bouchard, superintendent of the Red River Valley School Division, said the four boys who died attended two different rural schools in the area, Lowe Farm and Rosenort.
She said crisis counsellors were called in Wednesday to help staff and students get "through the day."
A "critical incident stress debrief" was also being set up to help the volunteer crews who responded, "so they can go through some of the emotions that come with a call like this," Schellenberg said.
"Our crews did the best they could with the conditions they had."
Groening said the children's deaths have hit the community hard. Help for the family was pouring in, including the offer of a house.
"I can only imagine what the parents are going through, what the three children who are saved are going through, how they are responding to the loss of four siblings," Groening said.
"It is a tragedy that will take a long time for them and for us to recover from."
— With files from John Cotter and Chris Purdy
Note to readers: This is a corrected story. An earlier version missed the last name of the president of Tri KoatingSuggest a correction