Two people, a man and a woman, were seriously injured in the explosion that rocked a home in Nelson Avenue, North End this afternoon. They have been taken to hospital for treatment.
The force of the blast destroyed the rear of the terraced home, flinging debris into the back gardens of homes to the rear, in Gladys Avenue.
Families in affected properties are being offered temporary accommodation by Portsmouth City Council.
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Andrew Payne lives in Gladys Avenue directly opposite the house where the explosion took place.
Describing the moment of the blast, the 70-year-old said: 'I heard this almighty "bang". There were shards of glass coming down and hitting the roof everywhere.
'I looked out and the whole back-end of the house had been blown out. Within four minutes, it was ablaze. I was gobsmacked.'
His wife Lynda, 69, said the experience was terrifying. She added: 'When the explosion happened, the whole house shook. It was like a bomb had gone off. It was this deep "thud" of an explosion.
'The whole house went up in flames. I have never seen anything go up so fast. It was terrifying.'
More than 20 firefighters from across the city were scrambled to the emergency.
They were joined by paramedics, an air ambulance crew and police.
Gladys Avenue was cordoned off as firefighters clambered through gardens to gain access to the rear of the exploded house.
The News understands that some nearby residents were evacuated as a safety precaution, while crews fought to contain the fire, while other emergency service workers carried out a headcount to check all other residents were accounted for.
Builder Gerald Saunders lives next door to the home that exploded and said it was home to a woman in her 70s and man in his 50s.
The 71-year-old added: ‘When the explosion happened it blew the front of the house off. The flames were 20ft high.’
Another witness, who asked not to be named, said: ‘I was standing outside four doors down. I saw the whole front of the house explode outward, both floors. It was very, very loud. I still feel shaken.’
Resident Paige Emery, 27, of Gladys Avenue, was in the bath when she heard the explosion. She said: ‘I heard a proper loud bang it was so loud and powerful it shook my whole house.
‘My housemate... then was banging on my bathroom door.
‘He saw the fire, called the fire brigade, the fire took about 20 minutes to put out in total.’
The explosion injured a man and a woman, South Central Ambulance Service said.
The service was called at 1.55pm with the Hampshire and Isle of Wight Air Ambulance and others treating both patients at the scene.
They are in a ‘serious condition’ and have been taken to Southampton General Hospital.
A spokeswoman said: ‘Both patients have been treated at the scene by all our crews and taken by ambulance accompanied by the ambulance crew and air ambulance crew, to University Hospital Southampton.
‘Our ambulance crews have left scene and our Hazardous Area Response Team and ambulance officers will remain on scene.’
She added: ‘We have sent to the scene our Hazardous Area Response Team (HART) four ambulance officers, two ambulance crews and the Hampshire and Isle of Wight Air Ambulance who have been working in partnership with Hampshire and Isle of Wight Fire Service, Hampshire Police, power companies and local authorities.’
Six road closures are currently in place across the area.
A spokesman for Hampshire police said: ‘We were called at 1.54pm this afternoon to a house fire at an address on Nelson Avenue, Portsmouth.
Officers are currently at the scene.
‘Road closures are in place on Nelson Avenue, Ophir Road, Oriel Road and Gladys Avenue from Northern Road up to North End Avenue.
‘The bottom of Cardiff Road, leading onto North End Road, is also closed.
‘We’re asking residents to please avoid the area at this time.
‘We will provide more information as soon as we can.’
Portsmouth North MP Penny Mordaunt tweeted: ‘My thoughts are with all those affected by the incident in Portsmouth today, in particular those injured.’
Gas network distributor SGN said it was ‘assisting the emergency services to ensure the immediate vicinity is made safe in our role as the gas emergency service’.
A city council statement said: ‘We have liaison officers and structural engineers on site to assist the fire service.
‘We are working to identify the status of other properties and residents to find out what support they need.
‘We have offered accommodation to families that we know we will be unable to return home.
‘Residents that are unable to park near their properties due to road closures can park at the nearby Mountbatten Leisure Centre car park.’