Two men have been injured in an explosion which sent the roof of a house flying into the road.
The blast at about 14:50 GMT in Silk Mill Drive, Tinshill, Leeds, destroyed the property's first floor and roof.
The men have been taken to hospital and are being treated for injuries which are not thought to be life threatening. No-one else was believed to be inside.
The cause of the explosion is not yet known but West Yorkshire Police said it was "not a terrorism related incident".
Gas engineer Allen Hart, 43, said: "It was so shocking, it was horrendous to see - the tiles from the roof had blown up in the air and had come down and stuck into the grass.
"All the roof was in the road, when the fire brigade came they had to drive over it.
"It was like a war zone."
Mr Hart said he was working further up the street fitting a boiler when he heard a "really loud bang". The explosion caused the property he was in to shake and the noise prompted him to go and see what had happened.
He said someone was lying down injured on the grass and he could smell gas - prompting him to call the gas emergency services straight away.
"I have never seen seen or experienced anything like that before," he added.
Northern Gas Networks confirmed its engineers were at the scene to help the emergency services to make the area safe.
David Hiley, who lives on the street, said: "I heard this big bang. I thought a plane had come down; my next-door neighbour ran out and she thought the same as me."
Neighbour Carole Webster said: "It was a massive explosion; it lasted a few seconds. It was horrendous."
A police spokesman said: "Road closures are in place and a neighbouring property has been evacuated due to structural damage. Enquiries are ongoing."