Emergency services were called to the property in Rosslyn Avenue, Ryhope, at just before 9am this morning.
It’s been said the explosion was not to be linked to terrorism, but the cause has not yet been confirmed.
Gentoo, the housing association which manages most of the city’s social housing stock, confirmed it was one of its properties.
It said staff were at the scene of the explosion offering support.
Pictures showed the property had been almost entirely destroyed by the blast.
The North East Ambulance Service said a woman was taken to hospital and was in a "serious but stable condition". The fire service then swept the property with specialist equipment and search dogs to ensure no one else was inside.
A neighbouring property was also severely affected by the explosion.
Graham Gowland, executive director of property at Gentoo Group, said: “We are aware of an incident that occurred at two of our properties on Rosslyn Avenue, in Ryhope.
“The safety of our residents is paramount and we have staff at the scene offering support.
“We are doing everything that we can and are working closely with the emergency services and all other parties involved while investigations are underway.”
This story will be updated.