"It feels like we have lost the last piece of our grandfather."
Mitai said she, her father, and other family members had been living in the house since the tangi.
She said a fire investigator had told her clothes that had just been in a drier were the likely cause of the fire.
"It was very much a freak accident. We arrived back at about 1.30pm to find the house engulfed in flames."
It was extinguished by 3.30pm, a fire spokesman said.
Mitai said all of her grandfather's possessions and wider family heirlooms were inside.
"My grandfather's original carvings, my grandmother's mere ... Everything was pretty much left as it was before both of them passed away.
"We have been able to save some photos but in terms of all the original artwork, my grandmother's statues and that, it has all been damaged.
"Plus the roof is collapsed, the floors in the end room have caved in. So now the house is deemed unliveable."
Neighbours came to hug her and offer help as Mitai spoke to the Rotorua Daily Post.
When asked if the home was insured, Mitai was doubtful.
"At this stage, we believe because of my grandfather passing away recently the house may not have been insured still."
Mina Mitai-Ngatai was awarded a Queen's Service Medal in 2015 for his services to Māori and the community.
He was renowned for performances with his "golden sax".
When the Rotorua Daily Post interviewed Mitai-Ngatai in 2010 he said his personal philosophy was "family's everything".
He was survived by four sons, four daughters plus whāngai [an adopted] son and daughter.
Mitai-Ngatai was the grandfather of 34 and great-grandfather to 31.
His wife Margaret died in 2002.