Dozens of firefighters battle a massive moorland blaze near Hebden Bridge.
The fire started in the hills between Hebden Bridge and Burnley.
A huge plume of smoke can be seen for miles.
Strong winds mean the 200m-long blaze is spreading quickly, firefighters said.
Teams from Greater Manchester and Lancashire are helping West Yorkshire firefighters.
A total of 40 firefighters and teams specializing in moorland fires are on the scene.
The fire started near the Widdop Reservoir in West Yorkshire, about seven miles east of Burnley and 10 miles north of Hebden Bridge.
Shaun Walton, Lancashire Fire and Rescure Service Group Director, tweeted: “Teams at @LancashireFRS are working closely with West Yorkshire FRS to deal with a large forest fire which appears to have started from Widdop Reservoir and has taken hold. spread extremely quickly as a blast caused by wind in the moors. “
A statement on the West Yorkshire Fire and Rescue Service website reads: “The moorland fire has now been scaled up to manufacture 8 pumps as well as several specialist forest fire apparatus and crews.
“There are appliances from West Yorkshire, Lancashire and GMC right now. “
It is not known at this stage what caused the fire.
In recent weeks, the UK fire and rescue services have repeatedly warned of the dangers of moorland fires, putting additional pressure on emergency services during the coronavirus lockdown.
The Greater Manchester Fire and Rescue Service said the number of ‘nuisance fires’ handled in the region more than doubled in the first week of the coronavirus lockdown.
During the seven days until March 29, firefighters were called in for 183 outdoor “nuisance fires” – officially known as deliberate secondary fires.
That’s more than double the 90 they processed in the week starting March 16.
Among the incidents were bonfires set by groups of teenagers, including campfires and trees, grass and garbage that were deliberately set on fire.