Images posted on social media showed one half of the semi-detached property in Rosslyn Avenue, Ryhope, reduced to a pile of rubble and significant damage to the second home, caused by the blast.
Ms Shepherd's sister Tracy Tia Judson said she was able to talk in the ambulance, having miraculously survived the major blast which sent roof tiles flying and shot the back door more than 20 metres down the back garden and over a fence.
Northumbria Police tweeted: "Police are aware of an explosion on Rosslyn Avenue, Sunderland".
Northumbria Police say it happened at a private residential house.
A North East Ambulance Service spokeswoman said one casualty suffering burns had been taken to Newcastle Royal Victoria Infirmary in a serious but stable condition.
Northern Gas Networks engineers were also on site.
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The company said it was "urgently" investigating the cause of the blast.
The emergency services said they were unable to give further details, including whether anyone was trapped in the rubble.
Emergency crews raced to the scene at around 8.50am after the blast left debris strewn across the road. He added: "I saw the window move and the house shook".
Tracey Pounder, 51, who lives in a neighbouring street, said: "I heard an almighty bang".
"Just had call off me Mam she's in shock as she's in Roselea [sic] Avenue".