Investigations are set to take several days

The blast wrecked the two-storey, semi-detached house in the Buckstone area of the capital.

Student Ross Gray, 20, was inside the property at the time. Emergency teams found him outside the house, suffering from burns to 50% of his body.

Specialist teams are now believed to be trying to pinpoint the source of a gas leak.

Utility company Scotland Gas Networks said its engineers were working with the police and experts from the Health and Safety Executive. Their investigations were expected to take several days.

Mr Gray was taken to a specialist burns unit at St John's Hospital in Livingston, West Lothian, where his condition was described as serious but stable.

Flames were coming out of the roof and windows

Two other people were treated at the scene by ambulance staff.

The first of about 40 firefighters to reach the blaze on Wednesday afternoon described flames coming out of the roof, windows and doors as they checked for casualties.

At the height of the outbreak there were eight fire units battling the flames. Most residents evacuated from their homes were now being allowed to return.

At least part of the damaged house will have to be demolished.