An explosion that left a man with life-threatening injuries was caused after a gas pipe was "deliberately tampered" with at a house, police have said.
The injured man was living on the second floor of the property in Wordsworth Road, Darlington, when the blast went off in February.
He is in a stable condition in hospital after the explosion which led to nearby properties being evacuated.
Police said the pipe in question was on the unoccupied ground floor.
A Durham Constabulary spokeswoman said: "We can confirm that the leak was caused by deliberate tampering of a gas pipe within the unoccupied ground floor flat of the property.
"Investigations are ongoing, with experts working to establish exactly how and when it happened."
One witness described the blast as like something from a "war film" while another said she heard a "big boom" and saw the street "light up".