Firefighters are battling a “rapidly” spreading fire on Ilkley Moor, on the hottest day of the year.
Some 50 acres are caught across two separate blazes, West Yorkshire Fire and Rescue Service said.
Images on social media show black smoke billowing from the sloped landscape, as crews from North Yorkshire and West Yorkshire Fire Services attend.
Flames have taken hold near Bingley, and also at Hanging Stone Road.
Bradford Council have asked people to stay away from the area.
No one is believed to have been hurt and investigators are looking into the cause of the fire.
Firefighters from 14 engines are using aqua backpacks, beaters and leaf blowers to extinguish the blaze, West Yorkshire Fire and Rescue Service said in a statement.
Crews have attended from Bingley, Shipley, Keighley and Rawdon, the service added.