The woman's former husband was still visibly upset but recalled driving past the scene earlier today and looked down towards his former wife's house but believed it was another house affected.
He said it wasn't until he got back to Hamilton and got a call from his daughter that he learned of the news.
Family had a brief chat with police at the cordon before leaving.
Fire Service northern communications manager Jaron Phillips said the Tirau property was engulfed by fire when a neighbour raised the alarm at 3.30am.
Phillips said four fire crews from Tirau, Putaruru and Matamata were needed to contain the blaze. A command unit from Rotorua is also at the scene.
Lakes District assistant area manager Hamish Smith said the front half of the house was engulfed in flames when the first crew arrived.
The bedrooms were in the back of the house, he said, with the living area, including the lounge, in the portion which was on fire.
A team of specialist fire investigators were now at the property to determine the cause of the fire.
Smith said they would have a briefing with police before fire safety investigators would enter the scene.
"We don't know a lot yet, we haven't even started the investigation process because have to treat the scene as a worst case scenario. So rather than us do our thing and police do their thing we will do it together.
"We're just in the process of assembling all the people we need to start the investigation."
Police said a scene guard was in place, with a scene examination due to get underway this morning. Detectives would be working alongside the fire investigators to establish the cause of the fire.
One neighbour said the woman lived there alone but often had family members stay.
She had previously lived in the house and said the lounge, kitchen and dining area filled the front half, while there were two bedrooms at the back, along with a bathroom.
Another neighbour, Lisette Dempsey, said it was bright, flashing lights of the fire trucks which woke her up.
A short time afterwards her and her husband heard several loud bangs which she thought might have been gas bottles.
"[The woman] would pop over and visit the neighbours across the road. She was quiet but she was a nice lady. I would often say good morning."