The family of four suffered from smoke inhalation – two were transported to Palmerston North Hospital to be treated.
Family friend Rebecca Madden is calling on Dannevirke locals to help provide clothes, blankets and other items to help the family upon return to the town.
"I'm so devastated. They've lost everything," she said. "I'm so glad they got out with no fatalities.
"I'm so grateful for all the community support. We are so lucky to live in a town that is so caring. When people are in need the overwhelming love and koha is amazing."
Police said a scene guard was put in place overnight and a scene examination undertaken on Sunday found nothing to indicate the fire was suspicious.
Madden said the 18-year-old and 11-year-old sons remained in hospital on Sunday. "They are all doing well, just majorly traumatised from the fire," she added.
Anybody willing to provide koha to the family can deliver items to Madden's house at 39 Christian St, Dannevirke.
Two fire trucks from Dannevirke attended the scene, with supporting water tankers from Norsewood and Ormondville.
Dannevirke local Sarah Jensen, who witnessed the fire, said she was made aware of the blaze after her brother, a volunteer firefighter, left the house in a rush.
"We could not only see the smoke from our deck, but also the glow of the flames," she said.
"I could even hear the windows popping and the radios from the engines."
Firefighters were also called to a shed fire in Hastings at 1.22pm on Saturday.
Two fire trucks from Hastings attended the scene on Southampton St W and successfully dealt with the blaze.
In a recent statement, Fire and Emergency New Zealand said May 2021 has been one of the worst months on record for fatal house fires.