An explosion at a terraced house in Seven Sisters "appears not to be gas work related", a company has said.
The incident in Church Road on Wednesday, June 24, resulted in two boys, aged five and two, being airlifted to Southmead Hospital in Bristol and a 31-year-old woman being taken to Morriston Hospital in Swansea.
Fourteen properties were evacuated and many residents described hearing a "massive bang" and seeing "a plume of dust and smoke".
Emergency services were called to the scene following the blast just after 2pm, while a former firefighter, who was one of the first people to arrive at the house, pulled the woman out of the rubble.
South Wales Police confirmed that the two boys remain in a "serious but stable" condition, while the woman, believed to be their mother, is in a "critical but stable" condition.
An investigation into the cause of the explosion carried out by GTC, an independent utility infrastructure and networks provider, has concluded that it does not appear "to be gas network related".
A spokesman for the firm said: "GTC engineers worked with the emergency services following last week’s incident to make the area safe and undertake an investigation into the cause.
"As a result of GTC’s investigation, it appears not to be gas network related."
Church Road remained closed following the incident as investigations were carried out.
An emergency team from Wales & West Utilities was sent to the scene on Wednesday and said that the explosion had caused "severe structural damage".
