Northumberland Police and the ambulance service confirmed they have been scrambled to the residential street.
The North East Ambulance Service confirmed: "We have been made aware of an incident at a private address on Rosslyn Avenue in Ryhope, Sunderland".
She said she saw two houses following the explosion, one of which was "completely flattened" and the other "pretty much in half".
Another wrote that she knew the house where the explosion went off: "It's across the road from old bingo hall".
Fire crews arriving at the scene entered the devastated property and did a "cracking job" assisted by ambulance crews, a senior officer said.
It's understood half of the home has been destroyed - and its roof has been "blown off".
Northern Gas Networks said its engineers were at the site and investigating "as a matter of urgency".
A house has been destroyed after an explosion in Sunderland..
A suspected gas explosion has left a property in ruins destroying half of a semi-detached house Credit North News NNP
One shop worker told Chronicle Live she heard "the loudest bang I have ever heard in my life".
People living in Rosslyn Avenue praised the rapid response by the emergency services.
"Half of the semi has gone and next door is wrecked".
Bill Forster, of Tyne and Wear Fire and Rescue Service, said: "The walls of the building have collapsed and the upper sections of the building have come down and the lady was trapped beneath that rubble".
North East Ambulance Service also confirmed they are now at the address.
Sean Hughes, 40, said he heard the explosion over a mile away.
A woman using the name Lauren x on Twitter said it sounded "like a bomb has exploded in ryhope; house literally shook".
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