Firefighters were yesterday sifting through the damaged building to try and find the cause.
Fourteen crews from Hampshire and Isle of Wight Fire Service rushed to Curdridge to tackle the blaze on Sunday, February 11.
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More than 60 firefighters worked through the night in Curdridge Lane, arriving around 7.30pm to find the roof and first floor of a property being engulfed by flames.
Worried neighbours arrived at the scene to see if they could help. However, there were no injuries with all the occupants having been safely evacuated.
Neighbour Phil Sommereux, a retired dentist, 64, who lives opposite, said: “We were watching a film when my wife stood up and said she could see flames and we realised it was a house on fire.
“I went over there to see if I could help. We didn’t know if anyone was trapped. I called the fire brigade on my way over.
“Luckily, everybody was out and the fire brigade was there. It was pretty dramatic. It’s certainly very upsetting for the owners who have been there for about 35 years.
“The fire had ripped through the roof. It was completely unexpected. We obviously feel very sorry for the owners who are now presumably homeless for some time.
“It was quite spectacular. I expect there will be a lot of support for them.”
A spokesperson for the fire service said: “Fourteen fire engines were in attendance at the height of the incident, along with the aerial ladder, specialist water carrier and environmental protection vehicles.
“Crews from Botley, Bishop’s Waltham, Hightown, Fareham, Eastleigh, Wickham, St Mary’s, Droxford, Cosham and Hamble were involved in the initial stages of the blaze.
“The electric and gas supplies to the property were isolated by engineers, as firefighters used hose reels and jets to extinguish the flames.
“USAR officers provided advice due to the property’s unstable structure following fire damage.
“The fire was surrounded shortly after midnight, when relief crews from Basingstoke, Alton, Hayling Island, Grayshott, Gosport, Rushmoor, Lymington and Horndean took over from the firefighters who were first on the scene.”
Yesterday morning, incident commander Simon Packer said: “The first floor and roof have completely gone and there is severe water damage to the ground floor.
“The fire investigation team is here now so that we can try and determine a cause.”
Crews remained on site and the road remained blocked for most of yesterday while firefighters dampened down.