The aftermath of the fire at the training area in Brecon Beacons (Picture: Wales News Service).
A US military aircraft has been blamed for a grass fire in the Brecon Beacons, covering the size of 200 football pitches.
The Osprey hovered over hot and dry grass during war games exercises, igniting a massive blaze on the Welsh mountainside.
"You can smell it when you drive through even with the windows closed."
The fire destroyed 150 hectares of grassland.
Crews from four fire stations and British troops from a nearby camp spent eight hours battling the fire which continued into the night on Epynt mountain.
The Sennybridge Training Area in mid-Wales is owned by the Ministry of Defence and is used for live fire military training.
Jane Element, from the nearby village of Tirabad, was stopped by another motorist who warned her about the fire.
She said: "He said there was a fire ahead and it had been caused by a helicopter taking off and scorching the grass.
"Further on there was a fire engine and I could see smoke was billowing across the road.
"The grass was very dry and it's been very hot so I'm not surprised, but it is amazing.
"You do see a lot of activity up the ranges but I didn't see a helicopter that day.
"The area where the fire was is about half a mile, by half a mile, it's just black, scorched grass.
"You can smell it when you drive through even with the windows closed.
"The grass was very dry and it's been very hot so I'm not surprised, but it is amazing."
Mid and West Wales Fire and Rescue Service said the grass was set alight by a hot downdraft from the aircraft during temperatures of 20c.
A spokesman said:
"The cause of the fire was attributed to a down draft from an American Osprey helicopter that was hovering above ground to deploy troops during an exercise at the military range."
Osprey helicopters use upright rotors which allows them to land and take off like a helicopter, and can also be used to fly at high speed and altitude.
Three types of Osprey aircraft are used in the USA, by the United States Marines Corps, the US Air Force and to transport President Donald Trump.
The MoD confirmed an American Osprey was taking part in a training mission and was deploying armed troops when the fire began.
A spokeswoman said:
"A grass fire started on the Sennybridge Training Area whilst an Osprey helicopter was carrying out routine training.
"An investigation is under way to identify the cause of the fire."