Debris from the explosion was scattered around the road

The emergency services were called to a maisonette in Hawkinge Gardens in the Ernesettle area of the city at about 0245 GMT on Friday.

Three people were injured. A 19-year-old woman and 23-year-old man were treated for shock at Derriford Hospital and later released.

An 18-year-old man suffered severe burns in the explosion has later moved from Derriford to a specialist unit in Bristol.

Debris scattered

The loud explosion blew part of the roof off, smashed several windows and started a fire, leaving the building badly damaged.

Debris from the building was scattered around in the road and surrounding gardens.

The flat on the ground floor was evacuated, the building cordoned off and the road closed.

An elderly woman who lives in the ground-floor flat has been told she cannot stay there and is now with friends.

Paramedics phoned

The 23-year-old occupant, Andrew Edwards, said: "There were sparks and all sorts coming out of the ceiling.

"I looked on the floor and I saw much of the ceiling was around my bed before I phoned paramedics."

The Health and Safety Executive and landlords Plymouth City Council have both begun investigations into the incident.

They are trying to establish if the cause was accidental or because of a failure in the gas supply system.

All that is known is that it was triggered when a light was switched on.

Building inspectors have to carry out a structural assessment to find out whether the building is safe or needs to be knocked down.