Three men have been held in connection with a large fire started on Ilkley Moor, West Yorkshire.
The blaze broke out on Saturday afternoon on the hottest day of the year in England, spreading rapidly across the dry terrain.
Around 70 firefighters were still working to bring the fire under control on Sunday morning, with authorities confirming a helicopter had also been deployed to assist with an "overhead water attack".
An investigation into the cause of the fire led to the arrests of three men, aged 19, 23 and 24, on Sunday afternoon, West Yorkshire Police said.
Locals posting updates to a community Facebook page have described the fire as "devastating".
Speaking to Sky News, Sarah Reed, who lives in the area, said it was a "shame for the wildlife" living on the moor.
She added: "The worst part is that this fire could have been prevented."
Ms Reed captured video footage of the flames as she drove past Ilkley Moor late on Saturday, which she later posted to Twitter.
Other videos posted by locals to community pages show thick smoke edging closer to inhabited areas.
"The smoke was pretty bad, but mainly blowing down the valley," Ms Reed said.
But once it had moved across the hillside, "the smoke started filling the town", she added.
Authorities warned people to stay away from the moor during another hot Easter day on Sunday.
In a tweet, Sergeant Terri Green said she had sent officers to cordon the area due to "dangerous conditions" caused by the fire.
Bradford Council confirmed a number of road closures.
Labour Party leader Jeremy Corbyn tweeted his thanks to those battling the blaze, before adding that the "awful scenes" on the moorlands served as a reminder for the "need to tackle climate change".
A wildfire also broke out in the Mourne Mountains in County Down, Northern Ireland, with more than 50 firefighters and 10 appliances battling the blaze.
The fire service said it was brought under control by Monday morning.
"Thank you to all our crews who worked tirelessly overnight to bring the gorse fire in the Mournes under control, all properties were protected and the caravan site reopened," tweeted @NIFRSWalmsley.
"Operations now scaled down, one crew remains on scene to deal with small flare ups."